Time.java revision f013e1afd1e68af5e3b868c26a653bbfb39538f8
1/* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.text.format; 18 19import android.content.res.Resources; 20 21import java.util.Locale; 22import java.util.TimeZone; 23 24/** 25 * The Time class is a faster replacement for the java.util.Calendar and 26 * java.util.GregorianCalendar classes. An instance of the Time class represents 27 * a moment in time, specified with second precision. It is modelled after 28 * struct tm, and in fact, uses struct tm to implement most of the 29 * functionality. 30 */ 31public class Time { 32 private static final String Y_M_D_T_H_M_S_000 = "%Y-%m-%dT%H:%M:%S.000"; 33 private static final String Y_M_D_T_H_M_S_000_Z = "%Y-%m-%dT%H:%M:%S.000Z"; 34 private static final String Y_M_D = "%Y-%m-%d"; 35 36 public static final String TIMEZONE_UTC = "UTC"; 37 38 /** 39 * The Julian day of the epoch, that is, January 1, 1970 on the Gregorian 40 * calendar. 41 */ 42 public static final int EPOCH_JULIAN_DAY = 2440588; 43 44 /** 45 * True if this is an allDay event. The hour, minute, second fields are 46 * all zero, and the date is displayed the same in all time zones. 47 */ 48 public boolean allDay; 49 50 /** 51 * Seconds [0-61] (2 leap seconds allowed) 52 */ 53 public int second; 54 55 /** 56 * Minute [0-59] 57 */ 58 public int minute; 59 60 /** 61 * Hour of day [0-23] 62 */ 63 public int hour; 64 65 /** 66 * Day of month [1-31] 67 */ 68 public int monthDay; 69 70 /** 71 * Month [0-11] 72 */ 73 public int month; 74 75 /** 76 * Year. TBD. Is this years since 1900 like in struct tm? 77 */ 78 public int year; 79 80 /** 81 * Day of week [0-6] 82 */ 83 public int weekDay; 84 85 /** 86 * Day of year [0-365] 87 */ 88 public int yearDay; 89 90 /** 91 * This time is in daylight savings time. One of: 92 * <ul> 93 * <li><b>positive</b> - in dst</li> 94 * <li><b>0</b> - not in dst</li> 95 * <li><b>negative</b> - unknown</li> 96 * </ul> 97 */ 98 public int isDst; 99 100 /** 101 * Offset from UTC (in seconds). 102 */ 103 public long gmtoff; 104 105 /** 106 * The timezone for this Time. Should not be null. 107 */ 108 public String timezone; 109 110 /* 111 * Define symbolic constants for accessing the fields in this class. Used in 112 * getActualMaximum(). 113 */ 114 public static final int SECOND = 1; 115 public static final int MINUTE = 2; 116 public static final int HOUR = 3; 117 public static final int MONTH_DAY = 4; 118 public static final int MONTH = 5; 119 public static final int YEAR = 6; 120 public static final int WEEK_DAY = 7; 121 public static final int YEAR_DAY = 8; 122 public static final int WEEK_NUM = 9; 123 124 public static final int SUNDAY = 0; 125 public static final int MONDAY = 1; 126 public static final int TUESDAY = 2; 127 public static final int WEDNESDAY = 3; 128 public static final int THURSDAY = 4; 129 public static final int FRIDAY = 5; 130 public static final int SATURDAY = 6; 131 132 /* 133 * The Locale for which date formatting strings have been loaded. 134 */ 135 private static Locale sLocale; 136 private static String[] sShortMonths; 137 private static String[] sLongMonths; 138 private static String[] sShortWeekdays; 139 private static String[] sLongWeekdays; 140 private static String sTimeOnlyFormat; 141 private static String sDateOnlyFormat; 142 private static String sDateTimeFormat; 143 private static String sAm; 144 private static String sPm; 145 private static String sDateCommand = "%a %b %e %H:%M:%S %Z %Y"; 146 147 /** 148 * Construct a Time object in the timezone named by the string 149 * argument "timezone". The time is initialized to Jan 1, 1970. 150 * @param timezone string containing the timezone to use. 151 * @see TimeZone 152 */ 153 public Time(String timezone) { 154 if (timezone == null) { 155 throw new NullPointerException("timezone is null!"); 156 } 157 this.timezone = timezone; 158 this.year = 1970; 159 this.monthDay = 1; 160 // Set the daylight-saving indicator to the unknown value -1 so that 161 // it will be recomputed. 162 this.isDst = -1; 163 } 164 165 /** 166 * Construct a Time object in the default timezone. The time is initialized to 167 * Jan 1, 1970. 168 */ 169 public Time() { 170 this(TimeZone.getDefault().getID()); 171 } 172 173 /** 174 * A copy constructor. Construct a Time object by copying the given 175 * Time object. No normalization occurs. 176 * 177 * @param other 178 */ 179 public Time(Time other) { 180 set(other); 181 } 182 183 /** 184 * Ensures the values in each field are in range. For example if the 185 * current value of this calendar is March 32, normalize() will convert it 186 * to April 1. It also fills in weekDay, yearDay, isDst and gmtoff. 187 * 188 * <p> 189 * If "ignoreDst" is true, then this method sets the "isDst" field to -1 190 * (the "unknown" value) before normalizing. It then computes the 191 * correct value for "isDst". 192 * 193 * <p> 194 * See {@link #toMillis(boolean)} for more information about when to 195 * use <tt>true</tt> or <tt>false</tt> for "ignoreDst". 196 * 197 * @return the UTC milliseconds since the epoch 198 */ 199 native public long normalize(boolean ignoreDst); 200 201 /** 202 * Convert this time object so the time represented remains the same, but is 203 * instead located in a different timezone. This method automatically calls 204 * normalize() in some cases 205 */ 206 native public void switchTimezone(String timezone); 207 208 private static final int[] DAYS_PER_MONTH = { 31, 28, 31, 30, 31, 30, 31, 209 31, 30, 31, 30, 31 }; 210 211 /** 212 * Return the maximum possible value for the given field given the value of 213 * the other fields. Requires that it be normalized for MONTH_DAY and 214 * YEAR_DAY. 215 * @param field one of the constants for HOUR, MINUTE, SECOND, etc. 216 * @return the maximum value for the field. 217 */ 218 public int getActualMaximum(int field) { 219 switch (field) { 220 case SECOND: 221 return 59; // leap seconds, bah humbug 222 case MINUTE: 223 return 59; 224 case HOUR: 225 return 23; 226 case MONTH_DAY: { 227 int n = DAYS_PER_MONTH[this.month]; 228 if (n != 28) { 229 return n; 230 } else { 231 int y = this.year; 232 return ((y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0)) ? 29 : 28; 233 } 234 } 235 case MONTH: 236 return 11; 237 case YEAR: 238 return 2037; 239 case WEEK_DAY: 240 return 6; 241 case YEAR_DAY: { 242 int y = this.year; 243 // Year days are numbered from 0, so the last one is usually 364. 244 return ((y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0)) ? 365 : 364; 245 } 246 case WEEK_NUM: 247 throw new RuntimeException("WEEK_NUM not implemented"); 248 default: 249 throw new RuntimeException("bad field=" + field); 250 } 251 } 252 253 /** 254 * Clears all values, setting the timezone to the given timezone. Sets isDst 255 * to a negative value to mean "unknown". 256 * @param timezone the timezone to use. 257 */ 258 public void clear(String timezone) { 259 if (timezone == null) { 260 throw new NullPointerException("timezone is null!"); 261 } 262 this.timezone = timezone; 263 this.allDay = false; 264 this.second = 0; 265 this.minute = 0; 266 this.hour = 0; 267 this.monthDay = 0; 268 this.month = 0; 269 this.year = 0; 270 this.weekDay = 0; 271 this.yearDay = 0; 272 this.gmtoff = 0; 273 this.isDst = -1; 274 } 275 276 /** 277 * return a negative number if a is less than b, a positive number if a is 278 * greater than b, and 0 if they are equal. 279 */ 280 native public static int compare(Time a, Time b); 281 282 /** 283 * Print the current value given the format string provided. See man 284 * strftime for what means what. The final string must be less than 256 285 * characters. 286 * @param format a string containing the desired format. 287 * @return a String containing the current time expressed in the current locale. 288 */ 289 public String format(String format) { 290 synchronized (Time.class) { 291 Locale locale = Locale.getDefault(); 292 293 if (sLocale == null || locale == null || !(locale.equals(sLocale))) { 294 Resources r = Resources.getSystem(); 295 296 sShortMonths = new String[] { 297 r.getString(com.android.internal.R.string.month_medium_january), 298 r.getString(com.android.internal.R.string.month_medium_february), 299 r.getString(com.android.internal.R.string.month_medium_march), 300 r.getString(com.android.internal.R.string.month_medium_april), 301 r.getString(com.android.internal.R.string.month_medium_may), 302 r.getString(com.android.internal.R.string.month_medium_june), 303 r.getString(com.android.internal.R.string.month_medium_july), 304 r.getString(com.android.internal.R.string.month_medium_august), 305 r.getString(com.android.internal.R.string.month_medium_september), 306 r.getString(com.android.internal.R.string.month_medium_october), 307 r.getString(com.android.internal.R.string.month_medium_november), 308 r.getString(com.android.internal.R.string.month_medium_december), 309 }; 310 sLongMonths = new String[] { 311 r.getString(com.android.internal.R.string.month_long_january), 312 r.getString(com.android.internal.R.string.month_long_february), 313 r.getString(com.android.internal.R.string.month_long_march), 314 r.getString(com.android.internal.R.string.month_long_april), 315 r.getString(com.android.internal.R.string.month_long_may), 316 r.getString(com.android.internal.R.string.month_long_june), 317 r.getString(com.android.internal.R.string.month_long_july), 318 r.getString(com.android.internal.R.string.month_long_august), 319 r.getString(com.android.internal.R.string.month_long_september), 320 r.getString(com.android.internal.R.string.month_long_october), 321 r.getString(com.android.internal.R.string.month_long_november), 322 r.getString(com.android.internal.R.string.month_long_december), 323 }; 324 sShortWeekdays = new String[] { 325 r.getString(com.android.internal.R.string.day_of_week_medium_sunday), 326 r.getString(com.android.internal.R.string.day_of_week_medium_monday), 327 r.getString(com.android.internal.R.string.day_of_week_medium_tuesday), 328 r.getString(com.android.internal.R.string.day_of_week_medium_wednesday), 329 r.getString(com.android.internal.R.string.day_of_week_medium_thursday), 330 r.getString(com.android.internal.R.string.day_of_week_medium_friday), 331 r.getString(com.android.internal.R.string.day_of_week_medium_saturday), 332 }; 333 sLongWeekdays = new String[] { 334 r.getString(com.android.internal.R.string.day_of_week_long_sunday), 335 r.getString(com.android.internal.R.string.day_of_week_long_monday), 336 r.getString(com.android.internal.R.string.day_of_week_long_tuesday), 337 r.getString(com.android.internal.R.string.day_of_week_long_wednesday), 338 r.getString(com.android.internal.R.string.day_of_week_long_thursday), 339 r.getString(com.android.internal.R.string.day_of_week_long_friday), 340 r.getString(com.android.internal.R.string.day_of_week_long_saturday), 341 }; 342 sTimeOnlyFormat = r.getString(com.android.internal.R.string.time_of_day); 343 sDateOnlyFormat = r.getString(com.android.internal.R.string.month_day_year); 344 sDateTimeFormat = r.getString(com.android.internal.R.string.date_and_time); 345 sAm = r.getString(com.android.internal.R.string.am); 346 sPm = r.getString(com.android.internal.R.string.pm); 347 348 sLocale = locale; 349 } 350 351 return format1(format); 352 } 353 } 354 355 native private String format1(String format); 356 357 /** 358 * Return the current time in YYYYMMDDTHHMMSS<tz> format 359 */ 360 @Override 361 native public String toString(); 362 363 /** 364 * Parses a date-time string in either the RFC 2445 format or an abbreviated 365 * format that does not include the "time" field. For example, all of the 366 * following strings are valid: 367 * 368 * <ul> 369 * <li>"20081013T160000Z"</li> 370 * <li>"20081013T160000"</li> 371 * <li>"20081013"</li> 372 * </ul> 373 * 374 * Returns whether or not the time is in UTC (ends with Z). If the string 375 * ends with "Z" then the timezone is set to UTC. If the date-time string 376 * included only a date and no time field, then the <code>allDay</code> 377 * field of this Time class is set to true and the <code>hour</code>, 378 * <code>minute</code>, and <code>second</code> fields are set to zero; 379 * otherwise (a time field was included in the date-time string) 380 * <code>allDay</code> is set to false. The fields <code>weekDay</code>, 381 * <code>yearDay</code>, and <code>gmtoff</code> are always set to zero, 382 * and the field <code>isDst</code> is set to -1 (unknown). To set those 383 * fields, call {@link #normalize(boolean)} after parsing. 384 * 385 * To parse a date-time string and convert it to UTC milliseconds, do 386 * something like this: 387 * 388 * <pre> 389 * Time time = new Time(); 390 * String date = "20081013T160000Z"; 391 * time.parse(date); 392 * long millis = time.normalize(false); 393 * </pre> 394 * 395 * @param s the string to parse 396 * @return true if the resulting time value is in UTC time 397 */ 398 public boolean parse(String s) { 399 if (nativeParse(s)) { 400 timezone = TIMEZONE_UTC; 401 return true; 402 } 403 return false; 404 } 405 406 /** 407 * Parse a time in the current zone in YYYYMMDDTHHMMSS format. 408 */ 409 native private boolean nativeParse(String s); 410 411 /** 412 * Parse a time in RFC 3339 format. This method also parses simple dates 413 * (that is, strings that contain no time or time offset). For example, 414 * all of the following strings are valid: 415 * 416 * <ul> 417 * <li>"2008-10-13T16:00:00.000Z"</li> 418 * <li>"2008-10-13T16:00:00.000+07:00"</li> 419 * <li>"2008-10-13T16:00:00.000-07:00"</li> 420 * <li>"2008-10-13"</li> 421 * </ul> 422 * 423 * <p> 424 * If the string contains a time and time offset, then the time offset will 425 * be used to convert the time value to UTC. 426 * </p> 427 * 428 * <p> 429 * If the given string contains just a date (with no time field), then 430 * the {@link #allDay} field is set to true and the {@link #hour}, 431 * {@link #minute}, and {@link #second} fields are set to zero. 432 * </p> 433 * 434 * <p> 435 * Returns true if the resulting time value is in UTC time. 436 * </p> 437 * 438 * @param s the string to parse 439 * @return true if the resulting time value is in UTC time 440 */ 441 public boolean parse3339(String s) { 442 if (nativeParse3339(s)) { 443 timezone = TIMEZONE_UTC; 444 return true; 445 } 446 return false; 447 } 448 449 native private boolean nativeParse3339(String s); 450 451 /** 452 * Returns the timezone string that is currently set for the device. 453 */ 454 public static String getCurrentTimezone() { 455 return TimeZone.getDefault().getID(); 456 } 457 458 /** 459 * Sets the time of the given Time object to the current time. 460 */ 461 native public void setToNow(); 462 463 /** 464 * Converts this time to milliseconds. Suitable for interacting with the 465 * standard java libraries. The time is in UTC milliseconds since the epoch. 466 * This does an implicit normalization to compute the milliseconds but does 467 * <em>not</em> change any of the fields in this Time object. If you want 468 * to normalize the fields in this Time object and also get the milliseconds 469 * then use {@link #normalize(boolean)}. 470 * 471 * <p> 472 * If "ignoreDst" is false, then this method uses the current setting of the 473 * "isDst" field and will adjust the returned time if the "isDst" field is 474 * wrong for the given time. See the sample code below for an example of 475 * this. 476 * 477 * <p> 478 * If "ignoreDst" is true, then this method ignores the current setting of 479 * the "isDst" field in this Time object and will instead figure out the 480 * correct value of "isDst" (as best it can) from the fields in this 481 * Time object. The only case where this method cannot figure out the 482 * correct value of the "isDst" field is when the time is inherently 483 * ambiguous because it falls in the hour that is repeated when switching 484 * from Daylight-Saving Time to Standard Time. 485 * 486 * <p> 487 * Here is an example where <tt>toMillis(true)</tt> adjusts the time, 488 * assuming that DST changes at 2am on Sunday, Nov 4, 2007. 489 * 490 * <pre> 491 * Time time = new Time(); 492 * time.set(2007, 10, 4); // set the date to Nov 4, 2007, 12am 493 * time.normalize(); // this sets isDst = 1 494 * time.monthDay += 1; // changes the date to Nov 5, 2007, 12am 495 * millis = time.toMillis(false); // millis is Nov 4, 2007, 11pm 496 * millis = time.toMillis(true); // millis is Nov 5, 2007, 12am 497 * </pre> 498 * 499 * <p> 500 * To avoid this problem, use <tt>toMillis(true)</tt> 501 * after adding or subtracting days or explicitly setting the "monthDay" 502 * field. On the other hand, if you are adding 503 * or subtracting hours or minutes, then you should use 504 * <tt>toMillis(false)</tt>. 505 * 506 * <p> 507 * You should also use <tt>toMillis(false)</tt> if you want 508 * to read back the same milliseconds that you set with {@link #set(long)} 509 * or {@link #set(Time)} or after parsing a date string. 510 */ 511 native public long toMillis(boolean ignoreDst); 512 513 /** 514 * Sets the fields in this Time object given the UTC milliseconds. After 515 * this method returns, all the fields are normalized. 516 * This also sets the "isDst" field to the correct value. 517 * 518 * @param millis the time in UTC milliseconds since the epoch. 519 */ 520 native public void set(long millis); 521 522 /** 523 * Format according to RFC 2445 DATETIME type. 524 * 525 * <p> 526 * The same as format("%Y%m%dT%H%M%S"). 527 */ 528 native public String format2445(); 529 530 /** 531 * Copy the value of that to this Time object. No normalization happens. 532 */ 533 public void set(Time that) { 534 this.timezone = that.timezone; 535 this.allDay = that.allDay; 536 this.second = that.second; 537 this.minute = that.minute; 538 this.hour = that.hour; 539 this.monthDay = that.monthDay; 540 this.month = that.month; 541 this.year = that.year; 542 this.weekDay = that.weekDay; 543 this.yearDay = that.yearDay; 544 this.isDst = that.isDst; 545 this.gmtoff = that.gmtoff; 546 } 547 548 /** 549 * Sets the fields. Sets weekDay, yearDay and gmtoff to 0, and isDst to -1. 550 * Call {@link #normalize(boolean)} if you need those. 551 */ 552 public void set(int second, int minute, int hour, int monthDay, int month, int year) { 553 this.allDay = false; 554 this.second = second; 555 this.minute = minute; 556 this.hour = hour; 557 this.monthDay = monthDay; 558 this.month = month; 559 this.year = year; 560 this.weekDay = 0; 561 this.yearDay = 0; 562 this.isDst = -1; 563 this.gmtoff = 0; 564 } 565 566 /** 567 * Sets the date from the given fields. Also sets allDay to true. 568 * Sets weekDay, yearDay and gmtoff to 0, and isDst to -1. 569 * Call {@link #normalize(boolean)} if you need those. 570 * 571 * @param monthDay the day of the month (in the range [1,31]) 572 * @param month the zero-based month number (in the range [0,11]) 573 * @param year the year 574 */ 575 public void set(int monthDay, int month, int year) { 576 this.allDay = true; 577 this.second = 0; 578 this.minute = 0; 579 this.hour = 0; 580 this.monthDay = monthDay; 581 this.month = month; 582 this.year = year; 583 this.weekDay = 0; 584 this.yearDay = 0; 585 this.isDst = -1; 586 this.gmtoff = 0; 587 } 588 589 /** 590 * Returns true if the time represented by this Time object occurs before 591 * the given time. 592 * 593 * @param that a given Time object to compare against 594 * @return true if this time is less than the given time 595 */ 596 public boolean before(Time that) { 597 return Time.compare(this, that) < 0; 598 } 599 600 601 /** 602 * Returns true if the time represented by this Time object occurs after 603 * the given time. 604 * 605 * @param that a given Time object to compare against 606 * @return true if this time is greater than the given time 607 */ 608 public boolean after(Time that) { 609 return Time.compare(this, that) > 0; 610 } 611 612 /** 613 * This array is indexed by the weekDay field (SUNDAY=0, MONDAY=1, etc.) 614 * and gives a number that can be added to the yearDay to give the 615 * closest Thursday yearDay. 616 */ 617 private static final int[] sThursdayOffset = { -3, 3, 2, 1, 0, -1, -2 }; 618 619 /** 620 * Computes the week number according to ISO 8601. The current Time 621 * object must already be normalized because this method uses the 622 * yearDay and weekDay fields. 623 * 624 * <p> 625 * In IS0 8601, weeks start on Monday. 626 * The first week of the year (week 1) is defined by ISO 8601 as the 627 * first week with four or more of its days in the starting year. 628 * Or equivalently, the week containing January 4. Or equivalently, 629 * the week with the year's first Thursday in it. 630 * </p> 631 * 632 * <p> 633 * The week number can be calculated by counting Thursdays. Week N 634 * contains the Nth Thursday of the year. 635 * </p> 636 * 637 * @return the ISO week number. 638 */ 639 public int getWeekNumber() { 640 // Get the year day for the closest Thursday 641 int closestThursday = yearDay + sThursdayOffset[weekDay]; 642 643 // Year days start at 0 644 if (closestThursday >= 0 && closestThursday <= 364) { 645 return closestThursday / 7 + 1; 646 } 647 648 // The week crosses a year boundary. 649 Time temp = new Time(this); 650 temp.monthDay += sThursdayOffset[weekDay]; 651 temp.normalize(true /* ignore isDst */); 652 return temp.yearDay / 7 + 1; 653 } 654 655 /** 656 * Return a string in the RFC 3339 format. 657 * <p> 658 * If allDay is true, expresses the time as Y-M-D</p> 659 * <p> 660 * Otherwise, if the timezone is UTC, expresses the time as Y-M-D-T-H-M-S UTC</p> 661 * <p> 662 * Otherwise the time is expressed the time as Y-M-D-T-H-M-S +- GMT</p> 663 * @param allDay 664 * @return string in the RFC 3339 format. 665 */ 666 public String format3339(boolean allDay) { 667 if (allDay) { 668 return format(Y_M_D); 669 } else if (TIMEZONE_UTC.equals(timezone)) { 670 return format(Y_M_D_T_H_M_S_000_Z); 671 } else { 672 String base = format(Y_M_D_T_H_M_S_000); 673 String sign = (gmtoff < 0) ? "-" : "+"; 674 int offset = (int)Math.abs(gmtoff); 675 int minutes = (offset % 3600) / 60; 676 int hours = offset / 3600; 677 678 return String.format("%s%s%02d:%02d", base, sign, hours, minutes); 679 } 680 } 681 682 /** 683 * Returns true if the day of the given time is the epoch on the Julian Calendar 684 * (January 1, 1970 on the Gregorian calendar). 685 * 686 * @param time the time to test 687 * @return true if epoch. 688 */ 689 public static boolean isEpoch(Time time) { 690 long millis = time.toMillis(true); 691 return getJulianDay(millis, 0) == EPOCH_JULIAN_DAY; 692 } 693 694 /** 695 * Computes the Julian day number, given the UTC milliseconds 696 * and the offset (in seconds) from UTC. The Julian day for a given 697 * date will be the same for every timezone. For example, the Julian 698 * day for July 1, 2008 is 2454649. This is the same value no matter 699 * what timezone is being used. The Julian day is useful for testing 700 * if two events occur on the same day and for determining the relative 701 * time of an event from the present ("yesterday", "3 days ago", etc.). 702 * 703 * <p> 704 * Use {@link #toMillis(boolean)} to get the milliseconds. 705 * 706 * @param millis the time in UTC milliseconds 707 * @param gmtoff the offset from UTC in seconds 708 * @return the Julian day 709 */ 710 public static int getJulianDay(long millis, long gmtoff) { 711 long offsetMillis = gmtoff * 1000; 712 long julianDay = (millis + offsetMillis) / DateUtils.DAY_IN_MILLIS; 713 return (int) julianDay + EPOCH_JULIAN_DAY; 714 } 715 716 /** 717 * <p>Sets the time from the given Julian day number, which must be based on 718 * the same timezone that is set in this Time object. The "gmtoff" field 719 * need not be initialized because the given Julian day may have a different 720 * GMT offset than whatever is currently stored in this Time object anyway. 721 * After this method returns all the fields will be normalized and the time 722 * will be set to 12am at the beginning of the given Julian day. 723 * </p> 724 * 725 * <p> 726 * The only exception to this is if 12am does not exist for that day because 727 * of daylight saving time. For example, Cairo, Eqypt moves time ahead one 728 * hour at 12am on April 25, 2008 and there are a few other places that 729 * also change daylight saving time at 12am. In those cases, the time 730 * will be set to 1am. 731 * </p> 732 * 733 * @param julianDay the Julian day in the timezone for this Time object 734 * @return the UTC milliseconds for the beginning of the Julian day 735 */ 736 public long setJulianDay(int julianDay) { 737 // Don't bother with the GMT offset since we don't know the correct 738 // value for the given Julian day. Just get close and then adjust 739 // the day. 740 long millis = (julianDay - EPOCH_JULIAN_DAY) * DateUtils.DAY_IN_MILLIS; 741 set(millis); 742 743 // Figure out how close we are to the requested Julian day. 744 // We can't be off by more than a day. 745 int approximateDay = getJulianDay(millis, gmtoff); 746 int diff = julianDay - approximateDay; 747 monthDay += diff; 748 749 // Set the time to 12am and re-normalize. 750 hour = 0; 751 minute = 0; 752 second = 0; 753 millis = normalize(true); 754 return millis; 755 } 756} 757