2 * Copyright (C) 1996-2011, International Business Machines
3 * Corporation and others. All Rights Reserved.
6 package com.ibm.icu.util;
9 import java.util.Locale;
11 import com.ibm.icu.util.ULocale.Category;
14 * {@icuenhanced java.util.GregorianCalendar}.{@icu _usage_}
16 * <p><code>GregorianCalendar</code> is a concrete subclass of
18 * and provides the standard calendar used by most of the world.
20 * <p>The standard (Gregorian) calendar has 2 eras, BC and AD.
22 * <p>This implementation handles a single discontinuity, which corresponds by
23 * default to the date the Gregorian calendar was instituted (October 15, 1582
24 * in some countries, later in others). The cutover date may be changed by the
25 * caller by calling <code>setGregorianChange()</code>.
27 * <p>Historically, in those countries which adopted the Gregorian calendar first,
28 * October 4, 1582 was thus followed by October 15, 1582. This calendar models
29 * this correctly. Before the Gregorian cutover, <code>GregorianCalendar</code>
30 * implements the Julian calendar. The only difference between the Gregorian
31 * and the Julian calendar is the leap year rule. The Julian calendar specifies
32 * leap years every four years, whereas the Gregorian calendar omits century
33 * years which are not divisible by 400.
35 * <p><code>GregorianCalendar</code> implements <em>proleptic</em> Gregorian and
36 * Julian calendars. That is, dates are computed by extrapolating the current
37 * rules indefinitely far backward and forward in time. As a result,
38 * <code>GregorianCalendar</code> may be used for all years to generate
39 * meaningful and consistent results. However, dates obtained using
40 * <code>GregorianCalendar</code> are historically accurate only from March 1, 4
41 * AD onward, when modern Julian calendar rules were adopted. Before this date,
42 * leap year rules were applied irregularly, and before 45 BC the Julian
43 * calendar did not even exist.
45 * <p>Prior to the institution of the Gregorian calendar, New Year's Day was
46 * March 25. To avoid confusion, this calendar always uses January 1. A manual
47 * adjustment may be made if desired for dates that are prior to the Gregorian
48 * changeover and which fall between January 1 and March 24.
50 * <p>Values calculated for the <code>WEEK_OF_YEAR</code> field range from 1 to
51 * 53. Week 1 for a year is the earliest seven day period starting on
52 * <code>getFirstDayOfWeek()</code> that contains at least
53 * <code>getMinimalDaysInFirstWeek()</code> days from that year. It thus
54 * depends on the values of <code>getMinimalDaysInFirstWeek()</code>,
55 * <code>getFirstDayOfWeek()</code>, and the day of the week of January 1.
56 * Weeks between week 1 of one year and week 1 of the following year are
57 * numbered sequentially from 2 to 52 or 53 (as needed).
59 * <p>For example, January 1, 1998 was a Thursday. If
60 * <code>getFirstDayOfWeek()</code> is <code>MONDAY</code> and
61 * <code>getMinimalDaysInFirstWeek()</code> is 4 (these are the values
62 * reflecting ISO 8601 and many national standards), then week 1 of 1998 starts
63 * on December 29, 1997, and ends on January 4, 1998. If, however,
64 * <code>getFirstDayOfWeek()</code> is <code>SUNDAY</code>, then week 1 of 1998
65 * starts on January 4, 1998, and ends on January 10, 1998; the first three days
66 * of 1998 then are part of week 53 of 1997.
68 * <p>Values calculated for the <code>WEEK_OF_MONTH</code> field range from 0 or
69 * 1 to 4 or 5. Week 1 of a month (the days with <code>WEEK_OF_MONTH =
70 * 1</code>) is the earliest set of at least
71 * <code>getMinimalDaysInFirstWeek()</code> contiguous days in that month,
72 * ending on the day before <code>getFirstDayOfWeek()</code>. Unlike
73 * week 1 of a year, week 1 of a month may be shorter than 7 days, need
74 * not start on <code>getFirstDayOfWeek()</code>, and will not include days of
75 * the previous month. Days of a month before week 1 have a
76 * <code>WEEK_OF_MONTH</code> of 0.
78 * <p>For example, if <code>getFirstDayOfWeek()</code> is <code>SUNDAY</code>
79 * and <code>getMinimalDaysInFirstWeek()</code> is 4, then the first week of
80 * January 1998 is Sunday, January 4 through Saturday, January 10. These days
81 * have a <code>WEEK_OF_MONTH</code> of 1. Thursday, January 1 through
82 * Saturday, January 3 have a <code>WEEK_OF_MONTH</code> of 0. If
83 * <code>getMinimalDaysInFirstWeek()</code> is changed to 3, then January 1
84 * through January 3 have a <code>WEEK_OF_MONTH</code> of 1.
87 * <strong>Example:</strong>
90 * // get the supported ids for GMT-08:00 (Pacific Standard Time)
91 * String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000);
92 * // if no ids were returned, something is wrong. get out.
93 * if (ids.length == 0)
97 * System.out.println("Current Time");
99 * // create a Pacific Standard Time time zone
100 * SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);
102 * // set up rules for daylight savings time
103 * pdt.setStartRule(Calendar.MARCH, 2, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
104 * pdt.setEndRule(Calendar.NOVEMBER, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
106 * // create a GregorianCalendar with the Pacific Daylight time zone
107 * // and the current date and time
108 * Calendar calendar = new GregorianCalendar(pdt);
109 * Date trialTime = new Date();
110 * calendar.setTime(trialTime);
112 * // print out a bunch of interesting things
113 * System.out.println("ERA: " + calendar.get(Calendar.ERA));
114 * System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
115 * System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
116 * System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
117 * System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
118 * System.out.println("DATE: " + calendar.get(Calendar.DATE));
119 * System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
120 * System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
121 * System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
122 * System.out.println("DAY_OF_WEEK_IN_MONTH: "
123 * + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
124 * System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
125 * System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
126 * System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
127 * System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
128 * System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
129 * System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
130 * System.out.println("ZONE_OFFSET: "
131 * + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
132 * System.out.println("DST_OFFSET: "
133 * + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000)));
135 * System.out.println("Current Time, with hour reset to 3");
136 * calendar.clear(Calendar.HOUR_OF_DAY); // so doesn't override
137 * calendar.set(Calendar.HOUR, 3);
138 * System.out.println("ERA: " + calendar.get(Calendar.ERA));
139 * System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
140 * System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
141 * System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
142 * System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
143 * System.out.println("DATE: " + calendar.get(Calendar.DATE));
144 * System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
145 * System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
146 * System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
147 * System.out.println("DAY_OF_WEEK_IN_MONTH: "
148 * + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
149 * System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
150 * System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
151 * System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
152 * System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
153 * System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
154 * System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
155 * System.out.println("ZONE_OFFSET: "
156 * + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000))); // in hours
157 * System.out.println("DST_OFFSET: "
158 * + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000))); // in hours</pre>
161 * GregorianCalendar usually should be instantiated using
162 * {@link com.ibm.icu.util.Calendar#getInstance(ULocale)} passing in a <code>ULocale</code>
163 * with the tag <code>"@calendar=gregorian"</code>.</p>
167 * @author David Goldsmith, Mark Davis, Chen-Lieh Huang, Alan Liu
170 public class GregorianCalendar extends Calendar {
171 // jdk1.4.2 serialver
172 private static final long serialVersionUID = 9199388694351062137L;
175 * Implementation Notes
177 * The Julian day number, as used here, is a modified number which has its
178 * onset at midnight, rather than noon.
180 * The epoch is the number of days or milliseconds from some defined
181 * starting point. The epoch for java.util.Date is used here; that is,
182 * milliseconds from January 1, 1970 (Gregorian), midnight UTC. Other
183 * epochs which are used are January 1, year 1 (Gregorian), which is day 1
184 * of the Gregorian calendar, and December 30, year 0 (Gregorian), which is
185 * day 1 of the Julian calendar.
187 * We implement the proleptic Julian and Gregorian calendars. This means we
188 * implement the modern definition of the calendar even though the
189 * historical usage differs. For example, if the Gregorian change is set
190 * to new Date(Long.MIN_VALUE), we have a pure Gregorian calendar which
191 * labels dates preceding the invention of the Gregorian calendar in 1582 as
192 * if the calendar existed then.
194 * Likewise, with the Julian calendar, we assume a consistent 4-year leap
195 * rule, even though the historical pattern of leap years is irregular,
196 * being every 3 years from 45 BC through 9 BC, then every 4 years from 8 AD
197 * onwards, with no leap years in-between. Thus date computations and
198 * functions such as isLeapYear() are not intended to be historically
201 * Given that milliseconds are a long, day numbers such as Julian day
202 * numbers, Gregorian or Julian calendar days, or epoch days, are also
203 * longs. Years can fit into an int.
211 * Value of the <code>ERA</code> field indicating
212 * the period before the common era (before Christ), also known as BCE.
213 * The sequence of years at the transition from <code>BC</code> to <code>AD</code> is
214 * ..., 2 BC, 1 BC, 1 AD, 2 AD,...
218 public static final int BC = 0;
221 * Value of the <code>ERA</code> field indicating
222 * the common era (Anno Domini), also known as CE.
223 * The sequence of years at the transition from <code>BC</code> to <code>AD</code> is
224 * ..., 2 BC, 1 BC, 1 AD, 2 AD,...
228 public static final int AD = 1;
230 private static final int EPOCH_YEAR = 1970;
232 private static final int[][] MONTH_COUNT = {
234 { 31, 31, 0, 0 }, // Jan
235 { 28, 29, 31, 31 }, // Feb
236 { 31, 31, 59, 60 }, // Mar
237 { 30, 30, 90, 91 }, // Apr
238 { 31, 31, 120, 121 }, // May
239 { 30, 30, 151, 152 }, // Jun
240 { 31, 31, 181, 182 }, // Jul
241 { 31, 31, 212, 213 }, // Aug
242 { 30, 30, 243, 244 }, // Sep
243 { 31, 31, 273, 274 }, // Oct
244 { 30, 30, 304, 305 }, // Nov
245 { 31, 31, 334, 335 } // Dec
246 // len length of month
247 // len2 length of month in a leap year
248 // st days in year before start of month
249 // st2 days in year before month in leap year
253 * Old year limits were least max 292269054, max 292278994.
255 private static final int LIMITS[][] = {
256 // Minimum Greatest Least Maximum
258 { 0, 0, 1, 1 }, // ERA
259 { 1, 1, 5828963, 5838270 }, // YEAR
260 { 0, 0, 11, 11 }, // MONTH
261 { 1, 1, 52, 53 }, // WEEK_OF_YEAR
262 {/* */}, // WEEK_OF_MONTH
263 { 1, 1, 28, 31 }, // DAY_OF_MONTH
264 { 1, 1, 365, 366 }, // DAY_OF_YEAR
265 {/* */}, // DAY_OF_WEEK
266 { -1, -1, 4, 5 }, // DAY_OF_WEEK_IN_MONTH
269 {/* */}, // HOUR_OF_DAY
272 {/* */}, // MILLISECOND
273 {/* */}, // ZONE_OFFSET
274 {/* */}, // DST_OFFSET
275 { -5838270, -5838270, 5828964, 5838271 }, // YEAR_WOY
276 {/* */}, // DOW_LOCAL
277 { -5838269, -5838269, 5828963, 5838270 }, // EXTENDED_YEAR
278 {/* */}, // JULIAN_DAY
279 {/* */}, // MILLISECONDS_IN_DAY
285 protected int handleGetLimit(int field, int limitType) {
286 return LIMITS[field][limitType];
289 /////////////////////
290 // Instance Variables
291 /////////////////////
294 * The point at which the Gregorian calendar rules are used, measured in
295 * milliseconds from the standard epoch. Default is October 15, 1582
296 * (Gregorian) 00:00:00 UTC or -12219292800000L. For this value, October 4,
297 * 1582 (Julian) is followed by October 15, 1582 (Gregorian). This
298 * corresponds to Julian day number 2299161.
301 private long gregorianCutover = -12219292800000L;
304 * Julian day number of the Gregorian cutover.
306 private transient int cutoverJulianDay = 2299161;
309 * The year of the gregorianCutover, with 0 representing
310 * 1 BC, -1 representing 2 BC, etc.
312 private transient int gregorianCutoverYear = 1582;
315 * Used by handleComputeJulianDay() and handleComputeMonthStart().
318 transient protected boolean isGregorian;
321 * Used by handleComputeJulianDay() and handleComputeMonthStart().
324 transient protected boolean invertGregorian;
331 * Constructs a default GregorianCalendar using the current time
332 * in the default time zone with the default <code>FORMAT</code> locale.
333 * @see Category#FORMAT
336 public GregorianCalendar() {
337 this(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
341 * Constructs a GregorianCalendar based on the current time
342 * in the given time zone with the default <code>FORMAT</code> locale.
343 * @param zone the given time zone.
344 * @see Category#FORMAT
347 public GregorianCalendar(TimeZone zone) {
348 this(zone, ULocale.getDefault(Category.FORMAT));
352 * Constructs a GregorianCalendar based on the current time
353 * in the default time zone with the given locale.
354 * @param aLocale the given locale.
357 public GregorianCalendar(Locale aLocale) {
358 this(TimeZone.getDefault(), aLocale);
362 * {@icu} Constructs a GregorianCalendar based on the current time
363 * in the default time zone with the given locale.
364 * @param locale the given ulocale.
367 public GregorianCalendar(ULocale locale) {
368 this(TimeZone.getDefault(), locale);
372 * {@icu} Constructs a GregorianCalendar based on the current time
373 * in the given time zone with the given locale.
374 * @param zone the given time zone.
375 * @param aLocale the given locale.
378 public GregorianCalendar(TimeZone zone, Locale aLocale) {
379 super(zone, aLocale);
380 setTimeInMillis(System.currentTimeMillis());
384 * Constructs a GregorianCalendar based on the current time
385 * in the given time zone with the given locale.
386 * @param zone the given time zone.
387 * @param locale the given ulocale.
390 public GregorianCalendar(TimeZone zone, ULocale locale) {
392 setTimeInMillis(System.currentTimeMillis());
396 * Constructs a GregorianCalendar with the given date set
397 * in the default time zone with the default <code>FORMAT</code> locale.
398 * @param year the value used to set the YEAR time field in the calendar.
399 * @param month the value used to set the MONTH time field in the calendar.
400 * Month value is 0-based. e.g., 0 for January.
401 * @param date the value used to set the DATE time field in the calendar.
402 * @see Category#FORMAT
405 public GregorianCalendar(int year, int month, int date) {
406 super(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
414 * Constructs a GregorianCalendar with the given date
415 * and time set for the default time zone with the default <code>FORMAT</code> locale.
416 * @param year the value used to set the YEAR time field in the calendar.
417 * @param month the value used to set the MONTH time field in the calendar.
418 * Month value is 0-based. e.g., 0 for January.
419 * @param date the value used to set the DATE time field in the calendar.
420 * @param hour the value used to set the HOUR_OF_DAY time field
422 * @param minute the value used to set the MINUTE time field
424 * @see Category#FORMAT
427 public GregorianCalendar(int year, int month, int date, int hour,
429 super(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
434 set(HOUR_OF_DAY, hour);
439 * Constructs a GregorianCalendar with the given date
440 * and time set for the default time zone with the default <code>FORMAT</code> locale.
441 * @param year the value used to set the YEAR time field in the calendar.
442 * @param month the value used to set the MONTH time field in the calendar.
443 * Month value is 0-based. e.g., 0 for January.
444 * @param date the value used to set the DATE time field in the calendar.
445 * @param hour the value used to set the HOUR_OF_DAY time field
447 * @param minute the value used to set the MINUTE time field
449 * @param second the value used to set the SECOND time field
451 * @see Category#FORMAT
454 public GregorianCalendar(int year, int month, int date, int hour,
455 int minute, int second) {
456 super(TimeZone.getDefault(), ULocale.getDefault(Category.FORMAT));
461 set(HOUR_OF_DAY, hour);
471 * Sets the GregorianCalendar change date. This is the point when the switch
472 * from Julian dates to Gregorian dates occurred. Default is October 15,
473 * 1582. Previous to this, dates will be in the Julian calendar.
475 * To obtain a pure Julian calendar, set the change date to
476 * <code>Date(Long.MAX_VALUE)</code>. To obtain a pure Gregorian calendar,
477 * set the change date to <code>Date(Long.MIN_VALUE)</code>.
479 * @param date the given Gregorian cutover date.
482 public void setGregorianChange(Date date) {
483 gregorianCutover = date.getTime();
485 // If the cutover has an extreme value, then create a pure
486 // Gregorian or pure Julian calendar by giving the cutover year and
487 // JD extreme values.
488 if (gregorianCutover <= MIN_MILLIS) {
489 gregorianCutoverYear = cutoverJulianDay = Integer.MIN_VALUE;
490 } else if (gregorianCutover >= MAX_MILLIS) {
491 gregorianCutoverYear = cutoverJulianDay = Integer.MAX_VALUE;
493 // Precompute two internal variables which we use to do the actual
494 // cutover computations. These are the Julian day of the cutover
495 // and the cutover year.
496 cutoverJulianDay = (int) floorDivide(gregorianCutover, ONE_DAY);
498 // Convert cutover millis to extended year
499 GregorianCalendar cal = new GregorianCalendar(getTimeZone());
501 gregorianCutoverYear = cal.get(EXTENDED_YEAR);
506 * Gets the Gregorian Calendar change date. This is the point when the
507 * switch from Julian dates to Gregorian dates occurred. Default is
508 * October 15, 1582. Previous to this, dates will be in the Julian
510 * @return the Gregorian cutover date for this calendar.
513 public final Date getGregorianChange() {
514 return new Date(gregorianCutover);
518 * Determines if the given year is a leap year. Returns true if the
519 * given year is a leap year.
520 * @param year the given year.
521 * @return true if the given year is a leap year; false otherwise.
524 public boolean isLeapYear(int year) {
525 return year >= gregorianCutoverYear ?
526 ((year%4 == 0) && ((year%100 != 0) || (year%400 == 0))) : // Gregorian
527 (year%4 == 0); // Julian
531 * Returns true if the given Calendar object is equivalent to this
532 * one. Calendar override.
534 * @param other the Calendar to be compared with this Calendar
537 public boolean isEquivalentTo(Calendar other) {
538 return super.isEquivalentTo(other) &&
539 gregorianCutover == ((GregorianCalendar)other).gregorianCutover;
544 * Generates the hash code for the GregorianCalendar object
547 public int hashCode() {
548 return super.hashCode() ^ (int)gregorianCutover;
552 * Roll a field by a signed amount.
555 public void roll(int field, int amount) {
560 // Unlike WEEK_OF_MONTH, WEEK_OF_YEAR never shifts the day of the
561 // week. Also, rolling the week of the year can have seemingly
562 // strange effects simply because the year of the week of year
563 // may be different from the calendar year. For example, the
564 // date Dec 28, 1997 is the first day of week 1 of 1998 (if
565 // weeks start on Sunday and the minimal days in first week is
567 int woy = get(WEEK_OF_YEAR);
568 // Get the ISO year, which matches the week of year. This
569 // may be one year before or after the calendar year.
570 int isoYear = get(YEAR_WOY);
571 int isoDoy = internalGet(DAY_OF_YEAR);
572 if (internalGet(MONTH) == Calendar.JANUARY) {
574 isoDoy += handleGetYearLength(isoYear);
578 isoDoy -= handleGetYearLength(isoYear - 1);
582 // Do fast checks to avoid unnecessary computation:
583 if (woy < 1 || woy > 52) {
584 // Determine the last week of the ISO year.
585 // We do this using the standard formula we use
586 // everywhere in this file. If we can see that the
587 // days at the end of the year are going to fall into
588 // week 1 of the next year, we drop the last week by
589 // subtracting 7 from the last day of the year.
590 int lastDoy = handleGetYearLength(isoYear);
591 int lastRelDow = (lastDoy - isoDoy + internalGet(DAY_OF_WEEK) -
592 getFirstDayOfWeek()) % 7;
593 if (lastRelDow < 0) lastRelDow += 7;
594 if ((6 - lastRelDow) >= getMinimalDaysInFirstWeek()) lastDoy -= 7;
595 int lastWoy = weekNumber(lastDoy, lastRelDow + 1);
596 woy = ((woy + lastWoy - 1) % lastWoy) + 1;
598 set(WEEK_OF_YEAR, woy);
599 set(YEAR, isoYear); // Why not YEAR_WOY? - Alan 11/6/00
604 super.roll(field, amount);
610 * Return the minimum value that this field could have, given the current date.
611 * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
614 public int getActualMinimum(int field) {
615 return getMinimum(field);
619 * Return the maximum value that this field could have, given the current date.
620 * For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual
621 * maximum would be 28; for "Feb 3, 1996" it s 29. Similarly for a Hebrew calendar,
622 * for some years the actual maximum for MONTH is 12, and for others 13.
625 public int getActualMaximum(int field) {
626 /* It is a known limitation that the code here (and in getActualMinimum)
627 * won't behave properly at the extreme limits of GregorianCalendar's
628 * representable range (except for the code that handles the YEAR
629 * field). That's because the ends of the representable range are at
630 * odd spots in the year. For calendars with the default Gregorian
631 * cutover, these limits are Sun Dec 02 16:47:04 GMT 292269055 BC to Sun
632 * Aug 17 07:12:55 GMT 292278994 AD, somewhat different for non-GMT
633 * zones. As a result, if the calendar is set to Aug 1 292278994 AD,
634 * the actual maximum of DAY_OF_MONTH is 17, not 30. If the date is Mar
635 * 31 in that year, the actual maximum month might be Jul, whereas is
636 * the date is Mar 15, the actual maximum might be Aug -- depending on
637 * the precise semantics that are desired. Similar considerations
638 * affect all fields. Nonetheless, this effect is sufficiently arcane
639 * that we permit it, rather than complicating the code to handle such
640 * intricacies. - liu 8/20/98
642 * UPDATE: No longer true, since we have pulled in the limit values on
643 * the year. - Liu 11/6/00 */
648 /* The year computation is no different, in principle, from the
649 * others, however, the range of possible maxima is large. In
650 * addition, the way we know we've exceeded the range is different.
651 * For these reasons, we use the special case code below to handle
654 * The actual maxima for YEAR depend on the type of calendar:
656 * Gregorian = May 17, 292275056 BC - Aug 17, 292278994 AD
657 * Julian = Dec 2, 292269055 BC - Jan 3, 292272993 AD
658 * Hybrid = Dec 2, 292269055 BC - Aug 17, 292278994 AD
660 * We know we've exceeded the maximum when either the month, date,
661 * time, or era changes in response to setting the year. We don't
662 * check for month, date, and time here because the year and era are
663 * sufficient to detect an invalid year setting. NOTE: If code is
664 * added to check the month and date in the future for some reason,
665 * Feb 29 must be allowed to shift to Mar 1 when setting the year.
668 Calendar cal = (Calendar) clone();
669 cal.setLenient(true);
671 int era = cal.get(ERA);
672 Date d = cal.getTime();
674 /* Perform a binary search, with the invariant that lowGood is a
675 * valid year, and highBad is an out of range year.
677 int lowGood = LIMITS[YEAR][1];
678 int highBad = LIMITS[YEAR][2]+1;
679 while ((lowGood + 1) < highBad) {
680 int y = (lowGood + highBad) / 2;
682 if (cal.get(YEAR) == y && cal.get(ERA) == era) {
686 cal.setTime(d); // Restore original fields
694 return super.getActualMaximum(field);
698 //////////////////////
699 // Proposed public API
700 //////////////////////
703 * Return true if the current time for this Calendar is in Daylignt
706 boolean inDaylightTime() {
707 if (!getTimeZone().useDaylightTime()) return false;
708 complete(); // Force update of DST_OFFSET field
709 return internalGet(DST_OFFSET) != 0;
713 /////////////////////
714 // Calendar framework
715 /////////////////////
720 protected int handleGetMonthLength(int extendedYear, int month) {
721 // If the month is out of range, adjust it into range, and
722 // modify the extended year value accordingly.
723 if (month < 0 || month > 11) {
724 int[] rem = new int[1];
725 extendedYear += floorDivide(month, 12, rem);
729 return MONTH_COUNT[month][isLeapYear(extendedYear)?1:0];
735 protected int handleGetYearLength(int eyear) {
736 return isLeapYear(eyear) ? 366 : 365;
739 /////////////////////////////
740 // Time => Fields computation
741 /////////////////////////////
744 * Override Calendar to compute several fields specific to the hybrid
745 * Gregorian-Julian calendar system. These are:
752 * <li>EXTENDED_YEAR</ul>
755 protected void handleComputeFields(int julianDay) {
756 int eyear, month, dayOfMonth, dayOfYear;
758 if (julianDay >= cutoverJulianDay) {
759 month = getGregorianMonth();
760 dayOfMonth = getGregorianDayOfMonth();
761 dayOfYear = getGregorianDayOfYear();
762 eyear = getGregorianYear();
764 // The Julian epoch day (not the same as Julian Day)
765 // is zero on Saturday December 30, 0 (Gregorian).
766 long julianEpochDay = julianDay - (JAN_1_1_JULIAN_DAY - 2);
767 eyear = (int) floorDivide(4*julianEpochDay + 1464, 1461);
769 // Compute the Julian calendar day number for January 1, eyear
770 long january1 = 365*(eyear-1) + floorDivide(eyear-1, 4);
771 dayOfYear = (int)(julianEpochDay - january1); // 0-based
773 // Julian leap years occurred historically every 4 years starting
774 // with 8 AD. Before 8 AD the spacing is irregular; every 3 years
775 // from 45 BC to 9 BC, and then none until 8 AD. However, we don't
776 // implement this historical detail; instead, we implement the
777 // computatinally cleaner proleptic calendar, which assumes
778 // consistent 4-year cycles throughout time.
779 boolean isLeap = ((eyear&0x3) == 0); // equiv. to (eyear%4 == 0)
781 // Common Julian/Gregorian calculation
783 int march1 = isLeap ? 60 : 59; // zero-based DOY for March 1
784 if (dayOfYear >= march1) {
785 correction = isLeap ? 1 : 2;
787 month = (12 * (dayOfYear + correction) + 6) / 367; // zero-based month
788 dayOfMonth = dayOfYear - MONTH_COUNT[month][isLeap?3:2] + 1; // one-based DOM
791 internalSet(MONTH, month);
792 internalSet(DAY_OF_MONTH, dayOfMonth);
793 internalSet(DAY_OF_YEAR, dayOfYear);
794 internalSet(EXTENDED_YEAR, eyear);
800 internalSet(ERA, era);
801 internalSet(YEAR, eyear);
804 /////////////////////////////
805 // Fields => Time computation
806 /////////////////////////////
811 protected int handleGetExtendedYear() {
813 if (newerField(EXTENDED_YEAR, YEAR) == EXTENDED_YEAR) {
814 year = internalGet(EXTENDED_YEAR, EPOCH_YEAR);
816 // The year defaults to the epoch start, the era to AD
817 int era = internalGet(ERA, AD);
819 year = 1 - internalGet(YEAR, 1); // Convert to extended year
821 year = internalGet(YEAR, EPOCH_YEAR);
830 protected int handleComputeJulianDay(int bestField) {
832 invertGregorian = false;
834 int jd = super.handleComputeJulianDay(bestField);
836 // The following check handles portions of the cutover year BEFORE the
837 // cutover itself happens.
838 if (isGregorian != (jd >= cutoverJulianDay)) {
839 invertGregorian = true;
840 jd = super.handleComputeJulianDay(bestField);
847 * Return JD of start of given month/year
850 protected int handleComputeMonthStart(int eyear, int month, boolean useMonth) {
852 // If the month is out of range, adjust it into range, and
853 // modify the extended year value accordingly.
854 if (month < 0 || month > 11) {
855 int[] rem = new int[1];
856 eyear += floorDivide(month, 12, rem);
860 boolean isLeap = eyear%4 == 0;
862 int julianDay = 365*y + floorDivide(y, 4) + (JAN_1_1_JULIAN_DAY - 3);
864 isGregorian = (eyear >= gregorianCutoverYear);
865 if (invertGregorian) {
866 isGregorian = !isGregorian;
869 isLeap = isLeap && ((eyear%100 != 0) || (eyear%400 == 0));
870 // Add 2 because Gregorian calendar starts 2 days after
872 julianDay += floorDivide(y, 400) - floorDivide(y, 100) + 2;
875 // At this point julianDay indicates the day BEFORE the first
876 // day of January 1, <eyear> of either the Julian or Gregorian
880 julianDay += MONTH_COUNT[month][isLeap?3:2];
887 * Return the current Calendar type.
888 * @return type of calendar
891 public String getType() {
896 private static CalendarFactory factory;
897 public static CalendarFactory factory() {
898 if (factory == null) {
899 factory = new CalendarFactory() {
900 public Calendar create(TimeZone tz, ULocale loc) {
901 return new GregorianCalendar(tz, loc);
904 public String factoryName() {