1 /* Copyright 2002-2022 CS GROUP
2 * Licensed to CS GROUP (CS) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * CS licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.orekit.time;
18
19 import java.io.Serializable;
20 import java.util.Date;
21 import java.util.TimeZone;
22
23 import org.hipparchus.util.FastMath;
24 import org.hipparchus.util.MathUtils;
25 import org.hipparchus.util.MathUtils.SumAndResidual;
26 import org.orekit.annotation.DefaultDataContext;
27 import org.orekit.data.DataContext;
28 import org.orekit.errors.OrekitException;
29 import org.orekit.errors.OrekitIllegalArgumentException;
30 import org.orekit.errors.OrekitMessages;
31 import org.orekit.utils.Constants;
32
33
34 /** This class represents a specific instant in time.
35
36 * <p>Instances of this class are considered to be absolute in the sense
37 * that each one represent the occurrence of some event and can be compared
38 * to other instances or located in <em>any</em> {@link TimeScale time scale}. In
39 * other words the different locations of an event with respect to two different
40 * time scales (say {@link TAIScale TAI} and {@link UTCScale UTC} for example) are
41 * simply different perspective related to a single object. Only one
42 * <code>AbsoluteDate</code> instance is needed, both representations being available
43 * from this single instance by specifying the time scales as parameter when calling
44 * the ad-hoc methods.</p>
45 *
46 * <p>Since an instance is not bound to a specific time-scale, all methods related
47 * to the location of the date within some time scale require to provide the time
48 * scale as an argument. It is therefore possible to define a date in one time scale
49 * and to use it in another one. An example of such use is to read a date from a file
50 * in UTC and write it in another file in TAI. This can be done as follows:</p>
51 * <pre>
52 * DateTimeComponents utcComponents = readNextDate();
53 * AbsoluteDate date = new AbsoluteDate(utcComponents, TimeScalesFactory.getUTC());
54 * writeNextDate(date.getComponents(TimeScalesFactory.getTAI()));
55 * </pre>
56 *
57 * <p>Two complementary views are available:</p>
58 * <ul>
59 * <li><p>location view (mainly for input/output or conversions)</p>
60 * <p>locations represent the coordinate of one event with respect to a
61 * {@link TimeScale time scale}. The related methods are {@link
62 * #AbsoluteDate(DateComponents, TimeComponents, TimeScale)}, {@link
63 * #AbsoluteDate(int, int, int, int, int, double, TimeScale)}, {@link
64 * #AbsoluteDate(int, int, int, TimeScale)}, {@link #AbsoluteDate(Date,
65 * TimeScale)}, {@link #parseCCSDSCalendarSegmentedTimeCode(byte, byte[])},
66 * {@link #toDate(TimeScale)}, {@link #toString(TimeScale) toString(timeScale)},
67 * {@link #toString()}, and {@link #timeScalesOffset}.</p>
68 * </li>
69 * <li><p>offset view (mainly for physical computation)</p>
70 * <p>offsets represent either the flow of time between two events
71 * (two instances of the class) or durations. They are counted in seconds,
72 * are continuous and could be measured using only a virtually perfect stopwatch.
73 * The related methods are {@link #AbsoluteDate(AbsoluteDate, double)},
74 * {@link #parseCCSDSUnsegmentedTimeCode(byte, byte, byte[], AbsoluteDate)},
75 * {@link #parseCCSDSDaySegmentedTimeCode(byte, byte[], DateComponents)},
76 * {@link #durationFrom(AbsoluteDate)}, {@link #compareTo(AbsoluteDate)}, {@link #equals(Object)}
77 * and {@link #hashCode()}.</p>
78 * </li>
79 * </ul>
80 * <p>
81 * A few reference epochs which are commonly used in space systems have been defined. These
82 * epochs can be used as the basis for offset computation. The supported epochs are:
83 * {@link #JULIAN_EPOCH}, {@link #MODIFIED_JULIAN_EPOCH}, {@link #FIFTIES_EPOCH},
84 * {@link #CCSDS_EPOCH}, {@link #GALILEO_EPOCH}, {@link #GPS_EPOCH}, {@link #QZSS_EPOCH}
85 * {@link #J2000_EPOCH}, {@link #JAVA_EPOCH}.
86 * There are also two factory methods {@link #createJulianEpoch(double)}
87 * and {@link #createBesselianEpoch(double)} that can be used to compute other reference
88 * epochs like J1900.0 or B1950.0.
89 * In addition to these reference epochs, two other constants are defined for convenience:
90 * {@link #PAST_INFINITY} and {@link #FUTURE_INFINITY}, which can be used either as dummy
91 * dates when a date is not yet initialized, or for initialization of loops searching for
92 * a min or max date.
93 * </p>
94 * <p>
95 * Instances of the <code>AbsoluteDate</code> class are guaranteed to be immutable.
96 * </p>
97 * @author Luc Maisonobe
98 * @author Evan Ward
99 * @see TimeScale
100 * @see TimeStamped
101 * @see ChronologicalComparator
102 */
103 public class AbsoluteDate
104 implements TimeStamped, TimeShiftable<AbsoluteDate>, Comparable<AbsoluteDate>, Serializable {
105
106 /** Reference epoch for julian dates: -4712-01-01T12:00:00 Terrestrial Time.
107 * <p>Both <code>java.util.Date</code> and {@link DateComponents} classes
108 * follow the astronomical conventions and consider a year 0 between
109 * years -1 and +1, hence this reference date lies in year -4712 and not
110 * in year -4713 as can be seen in other documents or programs that obey
111 * a different convention (for example the <code>convcal</code> utility).</p>
112 *
113 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
114 *
115 * @see TimeScales#getJulianEpoch()
116 */
117 @DefaultDataContext
118 public static final AbsoluteDate JULIAN_EPOCH =
119 DataContext.getDefault().getTimeScales().getJulianEpoch();
120
121 /** Reference epoch for modified julian dates: 1858-11-17T00:00:00 Terrestrial Time.
122 *
123 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
124 *
125 * @see TimeScales#getModifiedJulianEpoch()
126 */
127 @DefaultDataContext
128 public static final AbsoluteDate MODIFIED_JULIAN_EPOCH =
129 DataContext.getDefault().getTimeScales().getModifiedJulianEpoch();
130
131 /** Reference epoch for 1950 dates: 1950-01-01T00:00:00 Terrestrial Time.
132 *
133 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
134 *
135 * @see TimeScales#getFiftiesEpoch()
136 */
137 @DefaultDataContext
138 public static final AbsoluteDate FIFTIES_EPOCH =
139 DataContext.getDefault().getTimeScales().getFiftiesEpoch();
140
141 /** Reference epoch for CCSDS Time Code Format (CCSDS 301.0-B-4):
142 * 1958-01-01T00:00:00 International Atomic Time (<em>not</em> UTC).
143 *
144 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
145 *
146 * @see TimeScales#getCcsdsEpoch()
147 */
148 @DefaultDataContext
149 public static final AbsoluteDate CCSDS_EPOCH =
150 DataContext.getDefault().getTimeScales().getCcsdsEpoch();
151
152 /** Reference epoch for Galileo System Time: 1999-08-22T00:00:00 GST.
153 *
154 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
155 *
156 * @see TimeScales#getGalileoEpoch()
157 */
158 @DefaultDataContext
159 public static final AbsoluteDate GALILEO_EPOCH =
160 DataContext.getDefault().getTimeScales().getGalileoEpoch();
161
162 /** Reference epoch for GPS weeks: 1980-01-06T00:00:00 GPS time.
163 *
164 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
165 *
166 * @see TimeScales#getGpsEpoch()
167 */
168 @DefaultDataContext
169 public static final AbsoluteDate GPS_EPOCH =
170 DataContext.getDefault().getTimeScales().getGpsEpoch();
171
172 /** Reference epoch for QZSS weeks: 1980-01-06T00:00:00 QZSS time.
173 *
174 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
175 *
176 * @see TimeScales#getQzssEpoch()
177 */
178 @DefaultDataContext
179 public static final AbsoluteDate QZSS_EPOCH =
180 DataContext.getDefault().getTimeScales().getQzssEpoch();
181
182 /** Reference epoch for IRNSS weeks: 1999-08-22T00:00:00 IRNSS time.
183 *
184 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
185 *
186 * @see TimeScales#getIrnssEpoch()
187 */
188 @DefaultDataContext
189 public static final AbsoluteDate IRNSS_EPOCH =
190 DataContext.getDefault().getTimeScales().getIrnssEpoch();
191
192 /** Reference epoch for BeiDou weeks: 2006-01-01T00:00:00 UTC.
193 *
194 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
195 *
196 * @see TimeScales#getBeidouEpoch()
197 */
198 @DefaultDataContext
199 public static final AbsoluteDate BEIDOU_EPOCH =
200 DataContext.getDefault().getTimeScales().getBeidouEpoch();
201
202 /** Reference epoch for GLONASS four-year interval number: 1996-01-01T00:00:00 GLONASS time.
203 * <p>By convention, TGLONASS = UTC + 3 hours.</p>
204 *
205 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
206 *
207 * @see TimeScales#getGlonassEpoch()
208 */
209 @DefaultDataContext
210 public static final AbsoluteDate GLONASS_EPOCH =
211 DataContext.getDefault().getTimeScales().getGlonassEpoch();
212
213 /** J2000.0 Reference epoch: 2000-01-01T12:00:00 Terrestrial Time (<em>not</em> UTC).
214 * @see #createJulianEpoch(double)
215 * @see #createBesselianEpoch(double)
216 *
217 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
218 *
219 * @see TimeScales#getJ2000Epoch()
220 */
221 @DefaultDataContext
222 public static final AbsoluteDate J2000_EPOCH = // TODO
223 DataContext.getDefault().getTimeScales().getJ2000Epoch();
224
225 /** Java Reference epoch: 1970-01-01T00:00:00 Universal Time Coordinate.
226 * <p>
227 * Between 1968-02-01 and 1972-01-01, UTC-TAI = 4.213 170 0s + (MJD - 39 126) x 0.002 592s.
228 * As on 1970-01-01 MJD = 40587, UTC-TAI = 8.000082s
229 * </p>
230 *
231 * <p>This constant uses the {@link DataContext#getDefault() default data context}.
232 *
233 * @see TimeScales#getJavaEpoch()
234 */
235 @DefaultDataContext
236 public static final AbsoluteDate JAVA_EPOCH =
237 DataContext.getDefault().getTimeScales().getJavaEpoch();
238
239 /**
240 * An arbitrary finite date. Uses when a non-null date is needed but its value doesn't
241 * matter.
242 */
243 public static final AbsoluteDate ARBITRARY_EPOCH = new AbsoluteDate(0, 0);
244
245 /** Dummy date at infinity in the past direction.
246 * @see TimeScales#getPastInfinity()
247 */
248 public static final AbsoluteDate PAST_INFINITY = ARBITRARY_EPOCH.shiftedBy(Double.NEGATIVE_INFINITY);
249
250 /** Dummy date at infinity in the future direction.
251 * @see TimeScales#getFutureInfinity()
252 */
253 public static final AbsoluteDate FUTURE_INFINITY = ARBITRARY_EPOCH.shiftedBy(Double.POSITIVE_INFINITY);
254
255 /** Serializable UID. */
256 private static final long serialVersionUID = 617061803741806846L;
257
258 /** Reference epoch in seconds from 2000-01-01T12:00:00 TAI.
259 * <p>Beware, it is not {@link #J2000_EPOCH} since it is in TAI and not in TT.</p> */
260 private final long epoch;
261
262 /** Offset from the reference epoch in seconds. */
263 private final double offset;
264
265 /** Create an instance with a default value ({@link #J2000_EPOCH}).
266 *
267 * <p>This constructor uses the {@link DataContext#getDefault() default data context}.
268 *
269 * @see #AbsoluteDate(DateTimeComponents, TimeScale)
270 */
271 @DefaultDataContext
272 public AbsoluteDate() {
273 epoch = J2000_EPOCH.epoch;
274 offset = J2000_EPOCH.offset;
275 }
276
277 /** Build an instance from a location (parsed from a string) in a {@link TimeScale time scale}.
278 * <p>
279 * The supported formats for location are mainly the ones defined in ISO-8601 standard,
280 * the exact subset is explained in {@link DateTimeComponents#parseDateTime(String)},
281 * {@link DateComponents#parseDate(String)} and {@link TimeComponents#parseTime(String)}.
282 * </p>
283 * <p>
284 * As CCSDS ASCII calendar segmented time code is a trimmed down version of ISO-8601,
285 * it is also supported by this constructor.
286 * </p>
287 * @param location location in the time scale, must be in a supported format
288 * @param timeScale time scale
289 * @exception IllegalArgumentException if location string is not in a supported format
290 */
291 public AbsoluteDate(final String location, final TimeScale timeScale) {
292 this(DateTimeComponents.parseDateTime(location), timeScale);
293 }
294
295 /** Build an instance from a location in a {@link TimeScale time scale}.
296 * @param location location in the time scale
297 * @param timeScale time scale
298 */
299 public AbsoluteDate(final DateTimeComponents location, final TimeScale timeScale) {
300 this(location.getDate(), location.getTime(), timeScale);
301 }
302
303 /** Build an instance from a location in a {@link TimeScale time scale}.
304 * @param date date location in the time scale
305 * @param time time location in the time scale
306 * @param timeScale time scale
307 */
308 public AbsoluteDate(final DateComponents date, final TimeComponents time,
309 final TimeScale timeScale) {
310
311 final double seconds = time.getSecond();
312 final double tsOffset = timeScale.offsetToTAI(date, time);
313
314 // Use 2Sum for high precision.
315 final SumAndResidual sumAndResidual = MathUtils.twoSum(seconds, tsOffset);
316 final long dl = (long) FastMath.floor(sumAndResidual.getSum());
317
318 offset = (sumAndResidual.getSum() - dl) + sumAndResidual.getResidual();
319 epoch = 60l * ((date.getJ2000Day() * 24l + time.getHour()) * 60l +
320 time.getMinute() - time.getMinutesFromUTC() - 720l) + dl;
321
322 }
323
324 /** Build an instance from a location in a {@link TimeScale time scale}.
325 * @param year year number (may be 0 or negative for BC years)
326 * @param month month number from 1 to 12
327 * @param day day number from 1 to 31
328 * @param hour hour number from 0 to 23
329 * @param minute minute number from 0 to 59
330 * @param second second number from 0.0 to 60.0 (excluded)
331 * @param timeScale time scale
332 * @exception IllegalArgumentException if inconsistent arguments
333 * are given (parameters out of range)
334 */
335 public AbsoluteDate(final int year, final int month, final int day,
336 final int hour, final int minute, final double second,
337 final TimeScale timeScale) throws IllegalArgumentException {
338 this(new DateComponents(year, month, day), new TimeComponents(hour, minute, second), timeScale);
339 }
340
341 /** Build an instance from a location in a {@link TimeScale time scale}.
342 * @param year year number (may be 0 or negative for BC years)
343 * @param month month enumerate
344 * @param day day number from 1 to 31
345 * @param hour hour number from 0 to 23
346 * @param minute minute number from 0 to 59
347 * @param second second number from 0.0 to 60.0 (excluded)
348 * @param timeScale time scale
349 * @exception IllegalArgumentException if inconsistent arguments
350 * are given (parameters out of range)
351 */
352 public AbsoluteDate(final int year, final Month month, final int day,
353 final int hour, final int minute, final double second,
354 final TimeScale timeScale) throws IllegalArgumentException {
355 this(new DateComponents(year, month, day), new TimeComponents(hour, minute, second), timeScale);
356 }
357
358 /** Build an instance from a location in a {@link TimeScale time scale}.
359 * <p>The hour is set to 00:00:00.000.</p>
360 * @param date date location in the time scale
361 * @param timeScale time scale
362 * @exception IllegalArgumentException if inconsistent arguments
363 * are given (parameters out of range)
364 */
365 public AbsoluteDate(final DateComponents date, final TimeScale timeScale)
366 throws IllegalArgumentException {
367 this(date, TimeComponents.H00, timeScale);
368 }
369
370 /** Build an instance from a location in a {@link TimeScale time scale}.
371 * <p>The hour is set to 00:00:00.000.</p>
372 * @param year year number (may be 0 or negative for BC years)
373 * @param month month number from 1 to 12
374 * @param day day number from 1 to 31
375 * @param timeScale time scale
376 * @exception IllegalArgumentException if inconsistent arguments
377 * are given (parameters out of range)
378 */
379 public AbsoluteDate(final int year, final int month, final int day,
380 final TimeScale timeScale) throws IllegalArgumentException {
381 this(new DateComponents(year, month, day), TimeComponents.H00, timeScale);
382 }
383
384 /** Build an instance from a location in a {@link TimeScale time scale}.
385 * <p>The hour is set to 00:00:00.000.</p>
386 * @param year year number (may be 0 or negative for BC years)
387 * @param month month enumerate
388 * @param day day number from 1 to 31
389 * @param timeScale time scale
390 * @exception IllegalArgumentException if inconsistent arguments
391 * are given (parameters out of range)
392 */
393 public AbsoluteDate(final int year, final Month month, final int day,
394 final TimeScale timeScale) throws IllegalArgumentException {
395 this(new DateComponents(year, month, day), TimeComponents.H00, timeScale);
396 }
397
398 /** Build an instance from a location in a {@link TimeScale time scale}.
399 * @param location location in the time scale
400 * @param timeScale time scale
401 */
402 public AbsoluteDate(final Date location, final TimeScale timeScale) {
403 this(new DateComponents(DateComponents.JAVA_EPOCH,
404 (int) (location.getTime() / 86400000l)),
405 millisToTimeComponents((int) (location.getTime() % 86400000l)),
406 timeScale);
407 }
408
409 /** Build an instance from an elapsed duration since to another instant.
410 * <p>It is important to note that the elapsed duration is <em>not</em>
411 * the difference between two readings on a time scale. As an example,
412 * the duration between the two instants leading to the readings
413 * 2005-12-31T23:59:59 and 2006-01-01T00:00:00 in the {@link UTCScale UTC}
414 * time scale is <em>not</em> 1 second, but a stop watch would have measured
415 * an elapsed duration of 2 seconds between these two instances because a leap
416 * second was introduced at the end of 2005 in this time scale.</p>
417 * <p>This constructor is the reverse of the {@link #durationFrom(AbsoluteDate)}
418 * method.</p>
419 * @param since start instant of the measured duration
420 * @param elapsedDuration physically elapsed duration from the <code>since</code>
421 * instant, as measured in a regular time scale
422 * @see #durationFrom(AbsoluteDate)
423 */
424 public AbsoluteDate(final AbsoluteDate since, final double elapsedDuration) {
425 // Use 2Sum for high precision.
426 final SumAndResidual sumAndResidual = MathUtils.twoSum(since.offset, elapsedDuration);
427 if (Double.isInfinite(sumAndResidual.getSum())) {
428 offset = sumAndResidual.getSum();
429 epoch = (sumAndResidual.getSum() < 0) ? Long.MIN_VALUE : Long.MAX_VALUE;
430 } else {
431 final long dl = (long) FastMath.floor(sumAndResidual.getSum());
432 offset = (sumAndResidual.getSum() - dl) + sumAndResidual.getResidual();
433 epoch = since.epoch + dl;
434 }
435 }
436
437 /** Build an instance from an apparent clock offset with respect to another
438 * instant <em>in the perspective of a specific {@link TimeScale time scale}</em>.
439 * <p>It is important to note that the apparent clock offset <em>is</em> the
440 * difference between two readings on a time scale and <em>not</em> an elapsed
441 * duration. As an example, the apparent clock offset between the two instants
442 * leading to the readings 2005-12-31T23:59:59 and 2006-01-01T00:00:00 in the
443 * {@link UTCScale UTC} time scale is 1 second, but the elapsed duration is 2
444 * seconds because a leap second has been introduced at the end of 2005 in this
445 * time scale.</p>
446 * <p>This constructor is the reverse of the {@link #offsetFrom(AbsoluteDate,
447 * TimeScale)} method.</p>
448 * @param reference reference instant
449 * @param apparentOffset apparent clock offset from the reference instant
450 * (difference between two readings in the specified time scale)
451 * @param timeScale time scale with respect to which the offset is defined
452 * @see #offsetFrom(AbsoluteDate, TimeScale)
453 */
454 public AbsoluteDate(final AbsoluteDate reference, final double apparentOffset,
455 final TimeScale timeScale) {
456 this(new DateTimeComponents(reference.getComponents(timeScale), apparentOffset),
457 timeScale);
458 }
459
460 /** Build a date from its internal components.
461 * <p>
462 * This method is reserved for internal used (for example by {@link FieldAbsoluteDate}).
463 * </p>
464 * @param epoch reference epoch in seconds from 2000-01-01T12:00:00 TAI.
465 * (beware, it is not {@link #J2000_EPOCH} since it is in TAI and not in TT)
466 * @param offset offset from the reference epoch in seconds (must be
467 * between 0.0 included and 1.0 excluded)
468 * @since 9.0
469 */
470 AbsoluteDate(final long epoch, final double offset) {
471 this.epoch = epoch;
472 this.offset = offset;
473 }
474
475 /** Extract time components from a number of milliseconds within the day.
476 * @param millisInDay number of milliseconds within the day
477 * @return time components
478 */
479 private static TimeComponents millisToTimeComponents(final int millisInDay) {
480 return new TimeComponents(millisInDay / 1000, 0.001 * (millisInDay % 1000));
481 }
482
483 /** Get the reference epoch in seconds from 2000-01-01T12:00:00 TAI.
484 * <p>
485 * This method is reserved for internal used (for example by {@link FieldAbsoluteDate}).
486 * </p>
487 * <p>
488 * Beware, it is not {@link #J2000_EPOCH} since it is in TAI and not in TT.
489 * </p>
490 * @return reference epoch in seconds from 2000-01-01T12:00:00 TAI
491 * @since 9.0
492 */
493 long getEpoch() {
494 return epoch;
495 }
496
497 /** Get the offset from the reference epoch in seconds.
498 * <p>
499 * This method is reserved for internal used (for example by {@link FieldAbsoluteDate}).
500 * </p>
501 * @return offset from the reference epoch in seconds
502 * @since 9.0
503 */
504 double getOffset() {
505 return offset;
506 }
507
508 /** Build an instance from a CCSDS Unsegmented Time Code (CUC).
509 * <p>
510 * CCSDS Unsegmented Time Code is defined in the blue book:
511 * CCSDS Time Code Format (CCSDS 301.0-B-4) published in November 2010
512 * </p>
513 * <p>
514 * If the date to be parsed is formatted using version 3 of the standard
515 * (CCSDS 301.0-B-3 published in 2002) or if the extension of the preamble
516 * field introduced in version 4 of the standard is not used, then the
517 * {@code preambleField2} parameter can be set to 0.
518 * </p>
519 *
520 * <p>This method uses the {@link DataContext#getDefault() default data context} if
521 * the CCSDS epoch is used.
522 *
523 * @param preambleField1 first byte of the field specifying the format, often
524 * not transmitted in data interfaces, as it is constant for a given data interface
525 * @param preambleField2 second byte of the field specifying the format
526 * (added in revision 4 of the CCSDS standard in 2010), often not transmitted in data
527 * interfaces, as it is constant for a given data interface (value ignored if presence
528 * not signaled in {@code preambleField1})
529 * @param timeField byte array containing the time code
530 * @param agencyDefinedEpoch reference epoch, ignored if the preamble field
531 * specifies the {@link #CCSDS_EPOCH CCSDS reference epoch} is used (and hence
532 * may be null in this case)
533 * @return an instance corresponding to the specified date
534 * @see #parseCCSDSUnsegmentedTimeCode(byte, byte, byte[], AbsoluteDate, AbsoluteDate)
535 */
536 @DefaultDataContext
537 public static AbsoluteDate parseCCSDSUnsegmentedTimeCode(final byte preambleField1,
538 final byte preambleField2,
539 final byte[] timeField,
540 final AbsoluteDate agencyDefinedEpoch) {
541 return parseCCSDSUnsegmentedTimeCode(preambleField1, preambleField2, timeField,
542 agencyDefinedEpoch,
543 DataContext.getDefault().getTimeScales().getCcsdsEpoch());
544 }
545
546 /**
547 * Build an instance from a CCSDS Unsegmented Time Code (CUC).
548 * <p>
549 * CCSDS Unsegmented Time Code is defined in the blue book: CCSDS Time Code Format
550 * (CCSDS 301.0-B-4) published in November 2010
551 * </p>
552 * <p>
553 * If the date to be parsed is formatted using version 3 of the standard (CCSDS
554 * 301.0-B-3 published in 2002) or if the extension of the preamble field introduced
555 * in version 4 of the standard is not used, then the {@code preambleField2} parameter
556 * can be set to 0.
557 * </p>
558 *
559 * @param preambleField1 first byte of the field specifying the format, often not
560 * transmitted in data interfaces, as it is constant for a
561 * given data interface
562 * @param preambleField2 second byte of the field specifying the format (added in
563 * revision 4 of the CCSDS standard in 2010), often not
564 * transmitted in data interfaces, as it is constant for a
565 * given data interface (value ignored if presence not
566 * signaled in {@code preambleField1})
567 * @param timeField byte array containing the time code
568 * @param agencyDefinedEpoch reference epoch, ignored if the preamble field specifies
569 * the {@link #CCSDS_EPOCH CCSDS reference epoch} is used
570 * (and hence may be null in this case)
571 * @param ccsdsEpoch reference epoch, ignored if the preamble field specifies
572 * the agency epoch is used.
573 * @return an instance corresponding to the specified date
574 * @since 10.1
575 */
576 public static AbsoluteDate parseCCSDSUnsegmentedTimeCode(
577 final byte preambleField1,
578 final byte preambleField2,
579 final byte[] timeField,
580 final AbsoluteDate agencyDefinedEpoch,
581 final AbsoluteDate ccsdsEpoch) {
582
583 // time code identification and reference epoch
584 final AbsoluteDate epoch;
585 switch (preambleField1 & 0x70) {
586 case 0x10:
587 // the reference epoch is CCSDS epoch 1958-01-01T00:00:00 TAI
588 epoch = ccsdsEpoch;
589 break;
590 case 0x20:
591 // the reference epoch is agency defined
592 if (agencyDefinedEpoch == null) {
593 throw new OrekitException(OrekitMessages.CCSDS_DATE_MISSING_AGENCY_EPOCH);
594 }
595 epoch = agencyDefinedEpoch;
596 break;
597 default :
598 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_PREAMBLE_FIELD,
599 formatByte(preambleField1));
600 }
601
602 // time field lengths
603 int coarseTimeLength = 1 + ((preambleField1 & 0x0C) >>> 2);
604 int fineTimeLength = preambleField1 & 0x03;
605
606 if ((preambleField1 & 0x80) != 0x0) {
607 // there is an additional octet in preamble field
608 coarseTimeLength += (preambleField2 & 0x60) >>> 5;
609 fineTimeLength += (preambleField2 & 0x1C) >>> 2;
610 }
611
612 if (timeField.length != coarseTimeLength + fineTimeLength) {
613 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_LENGTH_TIME_FIELD,
614 timeField.length, coarseTimeLength + fineTimeLength);
615 }
616
617 double seconds = 0;
618 for (int i = 0; i < coarseTimeLength; ++i) {
619 seconds = seconds * 256 + toUnsigned(timeField[i]);
620 }
621 double subseconds = 0;
622 for (int i = timeField.length - 1; i >= coarseTimeLength; --i) {
623 subseconds = (subseconds + toUnsigned(timeField[i])) / 256;
624 }
625
626 return new AbsoluteDate(epoch, seconds).shiftedBy(subseconds);
627
628 }
629
630 /** Build an instance from a CCSDS Day Segmented Time Code (CDS).
631 * <p>
632 * CCSDS Day Segmented Time Code is defined in the blue book:
633 * CCSDS Time Code Format (CCSDS 301.0-B-4) published in November 2010
634 * </p>
635 *
636 * <p>This method uses the {@link DataContext#getDefault() default data context}.
637 *
638 * @param preambleField field specifying the format, often not transmitted in
639 * data interfaces, as it is constant for a given data interface
640 * @param timeField byte array containing the time code
641 * @param agencyDefinedEpoch reference epoch, ignored if the preamble field
642 * specifies the {@link #CCSDS_EPOCH CCSDS reference epoch} is used (and hence
643 * may be null in this case)
644 * @return an instance corresponding to the specified date
645 * @see #parseCCSDSDaySegmentedTimeCode(byte, byte[], DateComponents, TimeScale)
646 */
647 @DefaultDataContext
648 public static AbsoluteDate parseCCSDSDaySegmentedTimeCode(final byte preambleField, final byte[] timeField,
649 final DateComponents agencyDefinedEpoch) {
650 return parseCCSDSDaySegmentedTimeCode(preambleField, timeField,
651 agencyDefinedEpoch, DataContext.getDefault().getTimeScales().getUTC());
652 }
653
654 /** Build an instance from a CCSDS Day Segmented Time Code (CDS).
655 * <p>
656 * CCSDS Day Segmented Time Code is defined in the blue book:
657 * CCSDS Time Code Format (CCSDS 301.0-B-4) published in November 2010
658 * </p>
659 * @param preambleField field specifying the format, often not transmitted in
660 * data interfaces, as it is constant for a given data interface
661 * @param timeField byte array containing the time code
662 * @param agencyDefinedEpoch reference epoch, ignored if the preamble field
663 * specifies the {@link #CCSDS_EPOCH CCSDS reference epoch} is used (and hence
664 * may be null in this case)
665 * @param utc time scale used to compute date and time components.
666 * @return an instance corresponding to the specified date
667 * @since 10.1
668 */
669 public static AbsoluteDate parseCCSDSDaySegmentedTimeCode(
670 final byte preambleField,
671 final byte[] timeField,
672 final DateComponents agencyDefinedEpoch,
673 final TimeScale utc) {
674
675 // time code identification
676 if ((preambleField & 0xF0) != 0x40) {
677 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_PREAMBLE_FIELD,
678 formatByte(preambleField));
679 }
680
681 // reference epoch
682 final DateComponents epoch;
683 if ((preambleField & 0x08) == 0x00) {
684 // the reference epoch is CCSDS epoch 1958-01-01T00:00:00 TAI
685 epoch = DateComponents.CCSDS_EPOCH;
686 } else {
687 // the reference epoch is agency defined
688 if (agencyDefinedEpoch == null) {
689 throw new OrekitException(OrekitMessages.CCSDS_DATE_MISSING_AGENCY_EPOCH);
690 }
691 epoch = agencyDefinedEpoch;
692 }
693
694 // time field lengths
695 final int daySegmentLength = ((preambleField & 0x04) == 0x0) ? 2 : 3;
696 final int subMillisecondLength = (preambleField & 0x03) << 1;
697 if (subMillisecondLength == 6) {
698 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_PREAMBLE_FIELD,
699 formatByte(preambleField));
700 }
701 if (timeField.length != daySegmentLength + 4 + subMillisecondLength) {
702 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_LENGTH_TIME_FIELD,
703 timeField.length, daySegmentLength + 4 + subMillisecondLength);
704 }
705
706
707 int i = 0;
708 int day = 0;
709 while (i < daySegmentLength) {
710 day = day * 256 + toUnsigned(timeField[i++]);
711 }
712
713 long milliInDay = 0l;
714 while (i < daySegmentLength + 4) {
715 milliInDay = milliInDay * 256 + toUnsigned(timeField[i++]);
716 }
717 final int milli = (int) (milliInDay % 1000l);
718 final int seconds = (int) ((milliInDay - milli) / 1000l);
719
720 double subMilli = 0;
721 double divisor = 1;
722 while (i < timeField.length) {
723 subMilli = subMilli * 256 + toUnsigned(timeField[i++]);
724 divisor *= 1000;
725 }
726
727 final DateComponents date = new DateComponents(epoch, day);
728 final TimeComponents time = new TimeComponents(seconds);
729 return new AbsoluteDate(date, time, utc).shiftedBy(milli * 1.0e-3 + subMilli / divisor);
730
731 }
732
733 /** Build an instance from a CCSDS Calendar Segmented Time Code (CCS).
734 * <p>
735 * CCSDS Calendar Segmented Time Code is defined in the blue book:
736 * CCSDS Time Code Format (CCSDS 301.0-B-4) published in November 2010
737 * </p>
738 *
739 * <p>This method uses the {@link DataContext#getDefault() default data context}.
740 *
741 * @param preambleField field specifying the format, often not transmitted in
742 * data interfaces, as it is constant for a given data interface
743 * @param timeField byte array containing the time code
744 * @return an instance corresponding to the specified date
745 * @see #parseCCSDSCalendarSegmentedTimeCode(byte, byte[], TimeScale)
746 */
747 @DefaultDataContext
748 public static AbsoluteDate parseCCSDSCalendarSegmentedTimeCode(final byte preambleField, final byte[] timeField) {
749 return parseCCSDSCalendarSegmentedTimeCode(preambleField, timeField,
750 DataContext.getDefault().getTimeScales().getUTC());
751 }
752
753 /** Build an instance from a CCSDS Calendar Segmented Time Code (CCS).
754 * <p>
755 * CCSDS Calendar Segmented Time Code is defined in the blue book:
756 * CCSDS Time Code Format (CCSDS 301.0-B-4) published in November 2010
757 * </p>
758 * @param preambleField field specifying the format, often not transmitted in
759 * data interfaces, as it is constant for a given data interface
760 * @param timeField byte array containing the time code
761 * @param utc time scale used to compute date and time components.
762 * @return an instance corresponding to the specified date
763 * @since 10.1
764 */
765 public static AbsoluteDate parseCCSDSCalendarSegmentedTimeCode(
766 final byte preambleField,
767 final byte[] timeField,
768 final TimeScale utc) {
769
770 // time code identification
771 if ((preambleField & 0xF0) != 0x50) {
772 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_PREAMBLE_FIELD,
773 formatByte(preambleField));
774 }
775
776 // time field length
777 final int length = 7 + (preambleField & 0x07);
778 if (length == 14) {
779 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_PREAMBLE_FIELD,
780 formatByte(preambleField));
781 }
782 if (timeField.length != length) {
783 throw new OrekitException(OrekitMessages.CCSDS_DATE_INVALID_LENGTH_TIME_FIELD,
784 timeField.length, length);
785 }
786
787 // date part in the first four bytes
788 final DateComponents date;
789 if ((preambleField & 0x08) == 0x00) {
790 // month of year and day of month variation
791 date = new DateComponents(toUnsigned(timeField[0]) * 256 + toUnsigned(timeField[1]),
792 toUnsigned(timeField[2]),
793 toUnsigned(timeField[3]));
794 } else {
795 // day of year variation
796 date = new DateComponents(toUnsigned(timeField[0]) * 256 + toUnsigned(timeField[1]),
797 toUnsigned(timeField[2]) * 256 + toUnsigned(timeField[3]));
798 }
799
800 // time part from bytes 5 to last (between 7 and 13 depending on precision)
801 final TimeComponents time = new TimeComponents(toUnsigned(timeField[4]),
802 toUnsigned(timeField[5]),
803 toUnsigned(timeField[6]));
804 double subSecond = 0;
805 double divisor = 1;
806 for (int i = 7; i < length; ++i) {
807 subSecond = subSecond * 100 + toUnsigned(timeField[i]);
808 divisor *= 100;
809 }
810
811 return new AbsoluteDate(date, time, utc).shiftedBy(subSecond / divisor);
812
813 }
814
815 /** Decode a signed byte as an unsigned int value.
816 * @param b byte to decode
817 * @return an unsigned int value
818 */
819 private static int toUnsigned(final byte b) {
820 final int i = (int) b;
821 return (i < 0) ? 256 + i : i;
822 }
823
824 /** Format a byte as an hex string for error messages.
825 * @param data byte to format
826 * @return a formatted string
827 */
828 private static String formatByte(final byte data) {
829 return "0x" + Integer.toHexString(data).toUpperCase();
830 }
831
832 /** Build an instance corresponding to a Julian Day date.
833 * @param jd Julian day
834 * @param secondsSinceNoon seconds in the Julian day
835 * (BEWARE, Julian days start at noon, so 0.0 is noon)
836 * @param timeScale time scale in which the seconds in day are defined
837 * @return a new instant
838 */
839 public static AbsoluteDate createJDDate(final int jd, final double secondsSinceNoon,
840 final TimeScale timeScale) {
841 return new AbsoluteDate(new DateComponents(DateComponents.JULIAN_EPOCH, jd),
842 TimeComponents.H12, timeScale).shiftedBy(secondsSinceNoon);
843 }
844
845 /** Build an instance corresponding to a Modified Julian Day date.
846 * @param mjd modified Julian day
847 * @param secondsInDay seconds in the day
848 * @param timeScale time scale in which the seconds in day are defined
849 * @return a new instant
850 * @exception OrekitIllegalArgumentException if seconds number is out of range
851 */
852 public static AbsoluteDate createMJDDate(final int mjd, final double secondsInDay,
853 final TimeScale timeScale)
854 throws OrekitIllegalArgumentException {
855 final DateComponents dc = new DateComponents(DateComponents.MODIFIED_JULIAN_EPOCH, mjd);
856 final TimeComponents tc;
857 if (secondsInDay >= Constants.JULIAN_DAY) {
858 // check we are really allowed to use this number of seconds
859 final int secondsA = 86399; // 23:59:59, i.e. 59s in the last minute of the day
860 final double secondsB = secondsInDay - secondsA;
861 final TimeComponents safeTC = new TimeComponents(secondsA, 0.0);
862 final AbsoluteDate safeDate = new AbsoluteDate(dc, safeTC, timeScale);
863 if (timeScale.minuteDuration(safeDate) > 59 + secondsB) {
864 // we are within the last minute of the day, the number of seconds is OK
865 return safeDate.shiftedBy(secondsB);
866 } else {
867 // let TimeComponents trigger an OrekitIllegalArgumentException
868 // for the wrong number of seconds
869 tc = new TimeComponents(secondsA, secondsB);
870 }
871 } else {
872 tc = new TimeComponents(secondsInDay);
873 }
874
875 // create the date
876 return new AbsoluteDate(dc, tc, timeScale);
877
878 }
879
880
881 /** Build an instance corresponding to a Julian Epoch (JE).
882 * <p>According to Lieske paper: <a
883 * href="http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1979A%26A....73..282L&defaultprint=YES&filetype=.pdf.">
884 * Precession Matrix Based on IAU (1976) System of Astronomical Constants</a>, Astronomy and Astrophysics,
885 * vol. 73, no. 3, Mar. 1979, p. 282-284, Julian Epoch is related to Julian Ephemeris Date as:</p>
886 * <pre>
887 * JE = 2000.0 + (JED - 2451545.0) / 365.25
888 * </pre>
889 * <p>
890 * This method reverts the formula above and computes an {@code AbsoluteDate} from the Julian Epoch.
891 * </p>
892 *
893 * <p>This method uses the {@link DataContext#getDefault() default data context}.
894 *
895 * @param julianEpoch Julian epoch, like 2000.0 for defining the classical reference J2000.0
896 * @return a new instant
897 * @see #J2000_EPOCH
898 * @see #createBesselianEpoch(double)
899 * @see TimeScales#createJulianEpoch(double)
900 */
901 @DefaultDataContext
902 public static AbsoluteDate createJulianEpoch(final double julianEpoch) {
903 return DataContext.getDefault().getTimeScales().createJulianEpoch(julianEpoch);
904 }
905
906 /** Build an instance corresponding to a Besselian Epoch (BE).
907 * <p>According to Lieske paper: <a
908 * href="http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1979A%26A....73..282L&defaultprint=YES&filetype=.pdf.">
909 * Precession Matrix Based on IAU (1976) System of Astronomical Constants</a>, Astronomy and Astrophysics,
910 * vol. 73, no. 3, Mar. 1979, p. 282-284, Besselian Epoch is related to Julian Ephemeris Date as:</p>
911 * <pre>
912 * BE = 1900.0 + (JED - 2415020.31352) / 365.242198781
913 * </pre>
914 * <p>
915 * This method reverts the formula above and computes an {@code AbsoluteDate} from the Besselian Epoch.
916 * </p>
917 *
918 * <p>This method uses the {@link DataContext#getDefault() default data context}.
919 *
920 * @param besselianEpoch Besselian epoch, like 1950 for defining the classical reference B1950.0
921 * @return a new instant
922 * @see #createJulianEpoch(double)
923 * @see TimeScales#createBesselianEpoch(double)
924 */
925 @DefaultDataContext
926 public static AbsoluteDate createBesselianEpoch(final double besselianEpoch) {
927 return DataContext.getDefault().getTimeScales()
928 .createBesselianEpoch(besselianEpoch);
929 }
930
931 /** Get a time-shifted date.
932 * <p>
933 * Calling this method is equivalent to call <code>new AbsoluteDate(this, dt)</code>.
934 * </p>
935 * @param dt time shift in seconds
936 * @return a new date, shifted with respect to instance (which is immutable)
937 * @see org.orekit.utils.PVCoordinates#shiftedBy(double)
938 * @see org.orekit.attitudes.Attitude#shiftedBy(double)
939 * @see org.orekit.orbits.Orbit#shiftedBy(double)
940 * @see org.orekit.propagation.SpacecraftState#shiftedBy(double)
941 */
942 public AbsoluteDate shiftedBy(final double dt) {
943 return new AbsoluteDate(this, dt);
944 }
945
946 /** Compute the physically elapsed duration between two instants.
947 * <p>The returned duration is the number of seconds physically
948 * elapsed between the two instants, measured in a regular time
949 * scale with respect to surface of the Earth (i.e either the {@link
950 * TAIScale TAI scale}, the {@link TTScale TT scale} or the {@link
951 * GPSScale GPS scale}). It is the only method that gives a
952 * duration with a physical meaning.</p>
953 * <p>This method gives the same result (with less computation)
954 * as calling {@link #offsetFrom(AbsoluteDate, TimeScale)}
955 * with a second argument set to one of the regular scales cited
956 * above.</p>
957 * <p>This method is the reverse of the {@link #AbsoluteDate(AbsoluteDate,
958 * double)} constructor.</p>
959 * @param instant instant to subtract from the instance
960 * @return offset in seconds between the two instants (positive
961 * if the instance is posterior to the argument)
962 * @see #offsetFrom(AbsoluteDate, TimeScale)
963 * @see #AbsoluteDate(AbsoluteDate, double)
964 */
965 public double durationFrom(final AbsoluteDate instant) {
966 return (epoch - instant.epoch) + (offset - instant.offset);
967 }
968
969 /** Compute the apparent clock offset between two instant <em>in the
970 * perspective of a specific {@link TimeScale time scale}</em>.
971 * <p>The offset is the number of seconds counted in the given
972 * time scale between the locations of the two instants, with
973 * all time scale irregularities removed (i.e. considering all
974 * days are exactly 86400 seconds long). This method will give
975 * a result that may not have a physical meaning if the time scale
976 * is irregular. For example since a leap second was introduced at
977 * the end of 2005, the apparent offset between 2005-12-31T23:59:59
978 * and 2006-01-01T00:00:00 is 1 second, but the physical duration
979 * of the corresponding time interval as returned by the {@link
980 * #durationFrom(AbsoluteDate)} method is 2 seconds.</p>
981 * <p>This method is the reverse of the {@link #AbsoluteDate(AbsoluteDate,
982 * double, TimeScale)} constructor.</p>
983 * @param instant instant to subtract from the instance
984 * @param timeScale time scale with respect to which the offset should
985 * be computed
986 * @return apparent clock offset in seconds between the two instants
987 * (positive if the instance is posterior to the argument)
988 * @see #durationFrom(AbsoluteDate)
989 * @see #AbsoluteDate(AbsoluteDate, double, TimeScale)
990 */
991 public double offsetFrom(final AbsoluteDate instant, final TimeScale timeScale) {
992 final long elapsedDurationA = epoch - instant.epoch;
993 final double elapsedDurationB = (offset + timeScale.offsetFromTAI(this)) -
994 (instant.offset + timeScale.offsetFromTAI(instant));
995 return elapsedDurationA + elapsedDurationB;
996 }
997
998 /** Compute the offset between two time scales at the current instant.
999 * <p>The offset is defined as <i>l₁-l₂</i>
1000 * where <i>l₁</i> is the location of the instant in
1001 * the <code>scale1</code> time scale and <i>l₂</i> is the
1002 * location of the instant in the <code>scale2</code> time scale.</p>
1003 * @param scale1 first time scale
1004 * @param scale2 second time scale
1005 * @return offset in seconds between the two time scales at the
1006 * current instant
1007 */
1008 public double timeScalesOffset(final TimeScale scale1, final TimeScale scale2) {
1009 return scale1.offsetFromTAI(this) - scale2.offsetFromTAI(this);
1010 }
1011
1012 /** Convert the instance to a Java {@link java.util.Date Date}.
1013 * <p>Conversion to the Date class induces a loss of precision because
1014 * the Date class does not provide sub-millisecond information. Java Dates
1015 * are considered to be locations in some times scales.</p>
1016 * @param timeScale time scale to use
1017 * @return a {@link java.util.Date Date} instance representing the location
1018 * of the instant in the time scale
1019 */
1020 public Date toDate(final TimeScale timeScale) {
1021 final double time = epoch + (offset + timeScale.offsetFromTAI(this));
1022 return new Date(FastMath.round((time + 10957.5 * 86400.0) * 1000));
1023 }
1024
1025 /** Split the instance into date/time components.
1026 * @param timeScale time scale to use
1027 * @return date/time components
1028 */
1029 public DateTimeComponents getComponents(final TimeScale timeScale) {
1030
1031 if (Double.isInfinite(offset)) {
1032 // special handling for past and future infinity
1033 if (offset < 0) {
1034 return new DateTimeComponents(DateComponents.MIN_EPOCH, TimeComponents.H00);
1035 } else {
1036 return new DateTimeComponents(DateComponents.MAX_EPOCH,
1037 new TimeComponents(23, 59, 59.999));
1038 }
1039 }
1040
1041 // Compute offset from 2000-01-01T00:00:00 in specified time scale.
1042 // Use 2Sum for high precision.
1043 final double taiOffset = timeScale.offsetFromTAI(this);
1044 final SumAndResidual sumAndResidual = MathUtils.twoSum(offset, taiOffset);
1045
1046 // split date and time
1047 final long carry = (long) FastMath.floor(sumAndResidual.getSum());
1048 double offset2000B = (sumAndResidual.getSum() - carry) + sumAndResidual.getResidual();
1049 long offset2000A = epoch + carry + 43200l;
1050 if (offset2000B < 0) {
1051 offset2000A -= 1;
1052 offset2000B += 1;
1053 }
1054 long time = offset2000A % 86400l;
1055 if (time < 0l) {
1056 time += 86400l;
1057 }
1058 final int date = (int) ((offset2000A - time) / 86400l);
1059
1060 // extract calendar elements
1061 final DateComponents dateComponents = new DateComponents(DateComponents.J2000_EPOCH, date);
1062
1063 // extract time element, accounting for leap seconds
1064 final double leap = timeScale.insideLeap(this) ? timeScale.getLeap(this) : 0;
1065 final int minuteDuration = timeScale.minuteDuration(this);
1066 final TimeComponents timeComponents =
1067 TimeComponents.fromSeconds((int) time, offset2000B, leap, minuteDuration);
1068
1069 // build the components
1070 return new DateTimeComponents(dateComponents, timeComponents);
1071
1072 }
1073
1074 /** Split the instance into date/time components for a local time.
1075 *
1076 * <p>This method uses the {@link DataContext#getDefault() default data context}.
1077 *
1078 * @param minutesFromUTC offset in <em>minutes</em> from UTC (positive Eastwards UTC,
1079 * negative Westward UTC)
1080 * @return date/time components
1081 * @since 7.2
1082 * @see #getComponents(int, TimeScale)
1083 */
1084 @DefaultDataContext
1085 public DateTimeComponents getComponents(final int minutesFromUTC) {
1086 return getComponents(minutesFromUTC,
1087 DataContext.getDefault().getTimeScales().getUTC());
1088 }
1089
1090 /**
1091 * Split the instance into date/time components for a local time.
1092 *
1093 * @param minutesFromUTC offset in <em>minutes</em> from UTC (positive Eastwards UTC,
1094 * negative Westward UTC)
1095 * @param utc time scale used to compute date and time components.
1096 * @return date/time components
1097 * @since 10.1
1098 */
1099 public DateTimeComponents getComponents(final int minutesFromUTC,
1100 final TimeScale utc) {
1101
1102 final DateTimeComponents utcComponents = getComponents(utc);
1103
1104 // shift the date according to UTC offset, but WITHOUT touching the seconds,
1105 // as they may exceed 60.0 during a leap seconds introduction,
1106 // and we want to preserve these special cases
1107 final double seconds = utcComponents.getTime().getSecond();
1108
1109 int minute = utcComponents.getTime().getMinute() + minutesFromUTC;
1110 final int hourShift;
1111 if (minute < 0) {
1112 hourShift = (minute - 59) / 60;
1113 } else if (minute > 59) {
1114 hourShift = minute / 60;
1115 } else {
1116 hourShift = 0;
1117 }
1118 minute -= 60 * hourShift;
1119
1120 int hour = utcComponents.getTime().getHour() + hourShift;
1121 final int dayShift;
1122 if (hour < 0) {
1123 dayShift = (hour - 23) / 24;
1124 } else if (hour > 23) {
1125 dayShift = hour / 24;
1126 } else {
1127 dayShift = 0;
1128 }
1129 hour -= 24 * dayShift;
1130
1131 return new DateTimeComponents(new DateComponents(utcComponents.getDate(), dayShift),
1132 new TimeComponents(hour, minute, seconds, minutesFromUTC));
1133
1134 }
1135
1136 /** Split the instance into date/time components for a time zone.
1137 *
1138 * <p>This method uses the {@link DataContext#getDefault() default data context}.
1139 *
1140 * @param timeZone time zone
1141 * @return date/time components
1142 * @since 7.2
1143 * @see #getComponents(TimeZone, TimeScale)
1144 */
1145 @DefaultDataContext
1146 public DateTimeComponents getComponents(final TimeZone timeZone) {
1147 return getComponents(timeZone, DataContext.getDefault().getTimeScales().getUTC());
1148 }
1149
1150 /**
1151 * Split the instance into date/time components for a time zone.
1152 *
1153 * @param timeZone time zone
1154 * @param utc time scale used to computed date and time components.
1155 * @return date/time components
1156 * @since 10.1
1157 */
1158 public DateTimeComponents getComponents(final TimeZone timeZone,
1159 final TimeScale utc) {
1160 final AbsoluteDate javaEpoch = new AbsoluteDate(DateComponents.JAVA_EPOCH, utc);
1161 final long milliseconds = FastMath.round(1000 * offsetFrom(javaEpoch, utc));
1162 return getComponents(timeZone.getOffset(milliseconds) / 60000, utc);
1163 }
1164
1165 /** Compare the instance with another date.
1166 * @param date other date to compare the instance to
1167 * @return a negative integer, zero, or a positive integer as this date
1168 * is before, simultaneous, or after the specified date.
1169 */
1170 public int compareTo(final AbsoluteDate date) {
1171 final double duration = durationFrom(date);
1172 if (!Double.isNaN(duration)) {
1173 return Double.compare(duration, 0.0);
1174 }
1175 // both dates are infinity or one is NaN or both are NaN
1176 return Double.compare(offset, date.offset);
1177 }
1178
1179 /** {@inheritDoc} */
1180 public AbsoluteDate getDate() {
1181 return this;
1182 }
1183
1184 /** Check if the instance represents the same time as another instance.
1185 * @param date other date
1186 * @return true if the instance and the other date refer to the same instant
1187 */
1188 public boolean equals(final Object date) {
1189
1190 if (date == this) {
1191 // first fast check
1192 return true;
1193 }
1194
1195 if (date instanceof AbsoluteDate) {
1196 return durationFrom((AbsoluteDate) date) == 0;
1197 }
1198
1199 return false;
1200
1201 }
1202
1203 /** Check if the instance represents the same time as another.
1204 * @param other the instant to compare this date to
1205 * @return true if the instance and the argument refer to the same instant
1206 * @see #isCloseTo(TimeStamped, double)
1207 * @since 10.1
1208 */
1209 public boolean isEqualTo(final TimeStamped other) {
1210 return this.equals(other.getDate());
1211 }
1212
1213 /** Check if the instance time is close to another.
1214 * @param other the instant to compare this date to
1215 * @param tolerance the separation, in seconds, under which the two instants will be considered close to each other
1216 * @return true if the duration between the instance and the argument is strictly below the tolerance
1217 * @see #isEqualTo(TimeStamped)
1218 * @since 10.1
1219 */
1220 public boolean isCloseTo(final TimeStamped other, final double tolerance) {
1221 return FastMath.abs(this.durationFrom(other.getDate())) < tolerance;
1222 }
1223
1224 /** Check if the instance represents a time that is strictly before another.
1225 * @param other the instant to compare this date to
1226 * @return true if the instance is strictly before the argument when ordering chronologically
1227 * @see #isBeforeOrEqualTo(TimeStamped)
1228 * @since 10.1
1229 */
1230 public boolean isBefore(final TimeStamped other) {
1231 return this.compareTo(other.getDate()) < 0;
1232 }
1233
1234 /** Check if the instance represents a time that is strictly after another.
1235 * @param other the instant to compare this date to
1236 * @return true if the instance is strictly after the argument when ordering chronologically
1237 * @see #isAfterOrEqualTo(TimeStamped)
1238 * @since 10.1
1239 */
1240 public boolean isAfter(final TimeStamped other) {
1241 return this.compareTo(other.getDate()) > 0;
1242 }
1243
1244 /** Check if the instance represents a time that is before or equal to another.
1245 * @param other the instant to compare this date to
1246 * @return true if the instance is before (or equal to) the argument when ordering chronologically
1247 * @see #isBefore(TimeStamped)
1248 * @since 10.1
1249 */
1250 public boolean isBeforeOrEqualTo(final TimeStamped other) {
1251 return this.isEqualTo(other) || this.isBefore(other);
1252 }
1253
1254 /** Check if the instance represents a time that is after or equal to another.
1255 * @param other the instant to compare this date to
1256 * @return true if the instance is after (or equal to) the argument when ordering chronologically
1257 * @see #isAfterOrEqualTo(TimeStamped)
1258 * @since 10.1
1259 */
1260 public boolean isAfterOrEqualTo(final TimeStamped other) {
1261 return this.isEqualTo(other) || this.isAfter(other);
1262 }
1263
1264 /** Check if the instance represents a time that is strictly between two others representing
1265 * the boundaries of a time span. The two boundaries can be provided in any order: in other words,
1266 * whether <code>boundary</code> represents a time that is before or after <code>otherBoundary</code> will
1267 * not change the result of this method.
1268 * @param boundary one end of the time span
1269 * @param otherBoundary the other end of the time span
1270 * @return true if the instance is strictly between the two arguments when ordering chronologically
1271 * @see #isBetweenOrEqualTo(TimeStamped, TimeStamped)
1272 * @since 10.1
1273 */
1274 public boolean isBetween(final TimeStamped boundary, final TimeStamped otherBoundary) {
1275 final TimeStamped beginning;
1276 final TimeStamped end;
1277 if (boundary.getDate().isBefore(otherBoundary)) {
1278 beginning = boundary;
1279 end = otherBoundary;
1280 } else {
1281 beginning = otherBoundary;
1282 end = boundary;
1283 }
1284 return this.isAfter(beginning) && this.isBefore(end);
1285 }
1286
1287 /** Check if the instance represents a time that is between two others representing
1288 * the boundaries of a time span, or equal to one of them. The two boundaries can be provided in any order:
1289 * in other words, whether <code>boundary</code> represents a time that is before or after
1290 * <code>otherBoundary</code> will not change the result of this method.
1291 * @param boundary one end of the time span
1292 * @param otherBoundary the other end of the time span
1293 * @return true if the instance is between the two arguments (or equal to at least one of them)
1294 * when ordering chronologically
1295 * @see #isBetween(TimeStamped, TimeStamped)
1296 * @since 10.1
1297 */
1298 public boolean isBetweenOrEqualTo(final TimeStamped boundary, final TimeStamped otherBoundary) {
1299 return this.isEqualTo(boundary) || this.isEqualTo(otherBoundary) || this.isBetween(boundary, otherBoundary);
1300 }
1301
1302 /** Get a hashcode for this date.
1303 * @return hashcode
1304 */
1305 public int hashCode() {
1306 final long l = Double.doubleToLongBits(durationFrom(ARBITRARY_EPOCH));
1307 return (int) (l ^ (l >>> 32));
1308 }
1309
1310 /**
1311 * Get a String representation of the instant location with up to 16 digits of
1312 * precision for the seconds value.
1313 *
1314 * <p> Since this method is used in exception messages and error handling every
1315 * effort is made to return some representation of the instant. If UTC is available
1316 * from the default data context then it is used to format the string in UTC. If not
1317 * then TAI is used. Finally if the prior attempts fail this method falls back to
1318 * converting this class's internal representation to a string.
1319 *
1320 * <p>This method uses the {@link DataContext#getDefault() default data context}.
1321 *
1322 * @return a string representation of the instance, in ISO-8601 format if UTC is
1323 * available from the default data context.
1324 * @see #toString(TimeScale)
1325 * @see #toStringRfc3339(TimeScale)
1326 * @see DateTimeComponents#toString(int, int)
1327 */
1328 @DefaultDataContext
1329 public String toString() {
1330 // CHECKSTYLE: stop IllegalCatch check
1331 try {
1332 // try to use UTC first at that is likely most familiar to the user.
1333 return toString(DataContext.getDefault().getTimeScales().getUTC()) + "Z";
1334 } catch (RuntimeException e1) {
1335 // catch OrekitException, OrekitIllegalStateException, etc.
1336 try {
1337 // UTC failed, try to use TAI
1338 return toString(new TAIScale()) + " TAI";
1339 } catch (RuntimeException e2) {
1340 // catch OrekitException, OrekitIllegalStateException, etc.
1341 // Likely failed to convert to ymdhms.
1342 // Give user some indication of what time it is.
1343 try {
1344 return "(" + this.epoch + " + " + this.offset + ") seconds past epoch";
1345 } catch (RuntimeException e3) {
1346 // give up and throw an exception
1347 e2.addSuppressed(e3);
1348 e1.addSuppressed(e2);
1349 throw e1;
1350 }
1351 }
1352 }
1353 // CHECKSTYLE: resume IllegalCatch check
1354 }
1355
1356 /**
1357 * Get a String representation of the instant location in ISO-8601 format without the
1358 * UTC offset and with up to 16 digits of precision for the seconds value.
1359 *
1360 * @param timeScale time scale to use
1361 * @return a string representation of the instance.
1362 * @see #toStringRfc3339(TimeScale)
1363 * @see DateTimeComponents#toString(int, int)
1364 */
1365 public String toString(final TimeScale timeScale) {
1366 return getComponents(timeScale).toStringWithoutUtcOffset();
1367 }
1368
1369 /** Get a String representation of the instant location for a local time.
1370 *
1371 * <p>This method uses the {@link DataContext#getDefault() default data context}.
1372 *
1373 * @param minutesFromUTC offset in <em>minutes</em> from UTC (positive Eastwards UTC,
1374 * negative Westward UTC).
1375 * @return string representation of the instance,
1376 * in ISO-8601 format with milliseconds accuracy
1377 * @since 7.2
1378 * @see #toString(int, TimeScale)
1379 */
1380 @DefaultDataContext
1381 public String toString(final int minutesFromUTC) {
1382 return toString(minutesFromUTC,
1383 DataContext.getDefault().getTimeScales().getUTC());
1384 }
1385
1386 /**
1387 * Get a String representation of the instant location for a local time.
1388 *
1389 * @param minutesFromUTC offset in <em>minutes</em> from UTC (positive Eastwards UTC,
1390 * negative Westward UTC).
1391 * @param utc time scale used to compute date and time components.
1392 * @return string representation of the instance, in ISO-8601 format with milliseconds
1393 * accuracy
1394 * @since 10.1
1395 * @see #getComponents(int, TimeScale)
1396 * @see DateTimeComponents#toString(int, int)
1397 */
1398 public String toString(final int minutesFromUTC, final TimeScale utc) {
1399 final int minuteDuration = utc.minuteDuration(this);
1400 return getComponents(minutesFromUTC, utc).toString(minuteDuration);
1401 }
1402
1403 /** Get a String representation of the instant location for a time zone.
1404 *
1405 * <p>This method uses the {@link DataContext#getDefault() default data context}.
1406 *
1407 * @param timeZone time zone
1408 * @return string representation of the instance,
1409 * in ISO-8601 format with milliseconds accuracy
1410 * @since 7.2
1411 * @see #toString(TimeZone, TimeScale)
1412 */
1413 @DefaultDataContext
1414 public String toString(final TimeZone timeZone) {
1415 return toString(timeZone, DataContext.getDefault().getTimeScales().getUTC());
1416 }
1417
1418 /**
1419 * Get a String representation of the instant location for a time zone.
1420 *
1421 * @param timeZone time zone
1422 * @param utc time scale used to compute date and time components.
1423 * @return string representation of the instance, in ISO-8601 format with milliseconds
1424 * accuracy
1425 * @since 10.1
1426 * @see #getComponents(TimeZone, TimeScale)
1427 * @see DateTimeComponents#toString(int, int)
1428 */
1429 public String toString(final TimeZone timeZone, final TimeScale utc) {
1430 final int minuteDuration = utc.minuteDuration(this);
1431 return getComponents(timeZone, utc).toString(minuteDuration);
1432 }
1433
1434 /**
1435 * Represent the given date as a string according to the format in RFC 3339. RFC3339
1436 * is a restricted subset of ISO 8601 with a well defined grammar. Enough digits are
1437 * included in the seconds value to avoid rounding up to the next minute.
1438 *
1439 * <p>This method is different than {@link AbsoluteDate#toString(TimeScale)} in that
1440 * it includes a {@code "Z"} at the end to indicate the time zone and enough precision
1441 * to represent the point in time without rounding up to the next minute.
1442 *
1443 * <p>RFC3339 is unable to represent BC years, years of 10000 or more, time zone
1444 * offsets of 100 hours or more, or NaN. In these cases the value returned from this
1445 * method will not be valid RFC3339 format.
1446 *
1447 * @param utc time scale.
1448 * @return RFC 3339 format string.
1449 * @see <a href="https://tools.ietf.org/html/rfc3339#page-8">RFC 3339</a>
1450 * @see DateTimeComponents#toStringRfc3339()
1451 * @see #toString(TimeScale)
1452 * @see #getComponents(TimeScale)
1453 */
1454 public String toStringRfc3339(final TimeScale utc) {
1455 return this.getComponents(utc).toStringRfc3339();
1456 }
1457
1458 /**
1459 * Return a string representation of this date-time, rounded to the given precision.
1460 *
1461 * <p>The format used is ISO8601 without the UTC offset.</p>
1462 *
1463 * <p>Calling {@code toStringWithoutUtcOffset(DataContext.getDefault().getTimeScales().getUTC(),
1464 * 3)} will emulate the behavior of {@link #toString()} in Orekit 10 and earlier. Note
1465 * this method is more accurate as it correctly handles rounding during leap seconds.
1466 *
1467 * @param timeScale to use to compute components.
1468 * @param fractionDigits the number of digits to include after the decimal point in
1469 * the string representation of the seconds. The date and time
1470 * is first rounded as necessary. {@code fractionDigits} must be
1471 * greater than or equal to {@code 0}.
1472 * @return string representation of this date, time, and UTC offset
1473 * @see #toString(TimeScale)
1474 * @see #toStringRfc3339(TimeScale)
1475 * @see DateTimeComponents#toString(int, int)
1476 * @see DateTimeComponents#toStringWithoutUtcOffset(int, int)
1477 * @since 11.1
1478 */
1479 public String toStringWithoutUtcOffset(final TimeScale timeScale,
1480 final int fractionDigits) {
1481 return this.getComponents(timeScale)
1482 .toStringWithoutUtcOffset(timeScale.minuteDuration(this), fractionDigits);
1483 }
1484
1485 }