1 /* $selId: jewish.c,v 2.0 1995/10/24 01:13:06 lees Exp $
2 * Copyright 1993-1995, Scott E. Lee, all rights reserved.
3 * Permission granted to use, copy, modify, distribute and sell so long as
4 * the above copyright and this permission statement are retained in all
5 * copies. THERE IS NO WARRANTY - USE AT YOUR OWN RISK.
6 */
7
8 /**************************************************************************
9 *
10 * These are the externally visible components of this file:
11 *
12 * void
13 * SdnToJewish(
14 * long int sdn,
15 * int *pYear,
16 * int *pMonth,
17 * int *pDay);
18 *
19 * Convert a SDN to a Jewish calendar date. If the input SDN is before the
20 * first day of year 1, the three output values will all be set to zero,
21 * otherwise *pYear will be > 0; *pMonth will be in the range 1 to 13
22 * inclusive; *pDay will be in the range 1 to 30 inclusive. Note that Adar
23 * II is assigned the month number 7 and Elul is always 13.
24 *
25 * long int
26 * JewishToSdn(
27 * int year,
28 * int month,
29 * int day);
30 *
31 * Convert a Jewish calendar date to a SDN. Zero is returned when the
32 * input date is detected as invalid or out of the supported range. The
33 * return value will be > 0 for all valid, supported dates, but there are
34 * some invalid dates that will return a positive value. To verify that a
35 * date is valid, convert it to SDN and then back and compare with the
36 * original.
37 *
38 * char *JewishMonthName[14];
39 *
40 * Convert a Jewish month number (1 to 13) to the name of the Jewish month
41 * (null terminated). An index of zero will return a zero length string.
42 *
43 * VALID RANGE
44 *
45 * Although this software can handle dates all the way back to the year
46 * 1 (3761 B.C.), such use may not be meaningful.
47 *
48 * The Jewish calendar has been in use for several thousand years, but
49 * in the early days there was no formula to determine the start of a
50 * month. A new month was started when the new moon was first
51 * observed.
52 *
53 * It is not clear when the current rule based calendar replaced the
54 * observation based calendar. According to the book "Jewish Calendar
55 * Mystery Dispelled" by George Zinberg, the patriarch Hillel II
56 * published these rules in 358 A.D. But, according to The
57 * Encyclopedia Judaica, Hillel II may have only published the 19 year
58 * rule for determining the occurrence of leap years.
59 *
60 * I have yet to find a specific date when the current set of rules
61 * were known to be in use.
62 *
63 * CALENDAR OVERVIEW
64 *
65 * The Jewish calendar is based on lunar as well as solar cycles. A
66 * month always starts on or near a new moon and has either 29 or 30
67 * days (a lunar cycle is about 29 1/2 days). Twelve of these
68 * alternating 29-30 day months gives a year of 354 days, which is
69 * about 11 1/4 days short of a solar year.
70 *
71 * Since a month is defined to be a lunar cycle (new moon to new moon),
72 * this 11 1/4 day difference cannot be overcome by adding days to a
73 * month as with the Gregorian calendar, so an entire month is
74 * periodically added to the year, making some years 13 months long.
75 *
76 * For astronomical as well as ceremonial reasons, the start of a new
77 * year may be delayed until a day or two after the new moon causing
78 * years to vary in length. Leap years can be from 383 to 385 days and
79 * common years can be from 353 to 355 days. These are the months of
80 * the year and their possible lengths:
81 *
82 * COMMON YEAR LEAP YEAR
83 * 1 Tishri 30 30 30 30 30 30
84 * 2 Heshvan 29 29 30 29 29 30 (variable)
85 * 3 Kislev 29 30 30 29 30 30 (variable)
86 * 4 Tevet 29 29 29 29 29 29
87 * 5 Shevat 30 30 30 30 30 30
88 * 6 Adar I -- -- -- 30 30 30 (optional)
89 * 7 Adar (II) 29 29 29 29 29 29
90 * 8 Nisan 30 30 30 30 30 30
91 * 9 Iyyar 29 29 29 29 29 29
92 * 10 Sivan 30 30 30 30 30 30
93 * 11 Tammuz 29 29 29 29 29 29
94 * 12 Av 30 30 30 30 30 30
95 * 13 Elul 29 29 29 29 29 29
96 * --- --- --- --- --- ---
97 * 353 354 355 383 384 385
98 *
99 * Note that the month names and other words that appear in this file
100 * have multiple possible spellings in the Roman character set. I have
101 * chosen to use the spellings found in the Encyclopedia Judaica.
102 *
103 * Adar I, the month added for leap years, is sometimes referred to as
104 * the 13th month, but I have chosen to assign it the number 6 to keep
105 * the months in chronological order. This may not be consistent with
106 * other numbering schemes.
107 *
108 * Leap years occur in a fixed pattern of 19 years called the metonic
109 * cycle. The 3rd, 6th, 8th, 11th, 14th, 17th and 19th years of this
110 * cycle are leap years. The first metonic cycle starts with Jewish
111 * year 1, or 3761/60 B.C. This is believed to be the year of
112 * creation.
113 *
114 * To construct the calendar for a year, you must first find the length
115 * of the year by determining the first day of the year (Tishri 1, or
116 * Rosh Ha-Shanah) and the first day of the following year. This
117 * selects one of the six possible month length configurations listed
118 * above.
119 *
120 * Finding the first day of the year is the most difficult part.
121 * Finding the date and time of the new moon (or molad) is the first
122 * step. For this purpose, the lunar cycle is assumed to be 29 days 12
123 * hours and 793 halakim. A halakim is 1/1080th of an hour or 3 1/3
124 * seconds. (This assumed value is only about 1/2 second less than the
125 * value used by modern astronomers -- not bad for a number that was
126 * determined so long ago.) The first molad of year 1 occurred on
127 * Sunday at 11:20:11 P.M. This would actually be Monday, because the
128 * Jewish day is considered to begin at sunset.
129 *
130 * Since sunset varies, the day is assumed to begin at 6:00 P.M. for
131 * calendar calculation purposes. So, the first molad was 5 hours 793
132 * halakim after the start of Tishri 1, 0001 (which was Monday
133 * September 7, 4761 B.C. by the Gregorian calendar). All subsequent
134 * molads can be calculated from this starting point by adding the
135 * length of a lunar cycle.
136 *
137 * Once the molad that starts a year is determined the actual start of
138 * the year (Tishri 1) can be determined. Tishri 1 will be the day of
139 * the molad unless it is delayed by one of the following four rules
140 * (called dehiyyot). Each rule can delay the start of the year by one
141 * day, and since rule #1 can combine with one of the other rules, it
142 * can be delayed as much as two days.
143 *
144 * 1. Tishri 1 must never be Sunday, Wednesday or Friday. (This
145 * is largely to prevent certain holidays from occurring on the
146 * day before or after the Sabbath.)
147 *
148 * 2. If the molad occurs on or after noon, Tishri 1 must be
149 * delayed.
150 *
151 * 3. If it is a common (not leap) year and the molad occurs on
152 * Tuesday at or after 3:11:20 A.M., Tishri 1 must be delayed.
153 *
154 * 4. If it is the year following a leap year and the molad occurs
155 * on Monday at or after 9:32:43 and 1/3 sec, Tishri 1 must be
156 * delayed.
157 *
158 * GLOSSARY
159 *
160 * dehiyyot The set of 4 rules that determine when the new year
161 * starts relative to the molad.
162 *
163 * halakim 1/1080th of an hour or 3 1/3 seconds.
164 *
165 * lunar cycle The period of time between mean conjunctions of the
166 * sun and moon (new moon to new moon). This is
167 * assumed to be 29 days 12 hours and 793 halakim for
168 * calendar purposes.
169 *
170 * metonic cycle A 19 year cycle which determines which years are
171 * leap years and which are common years. The 3rd,
172 * 6th, 8th, 11th, 14th, 17th and 19th years of this
173 * cycle are leap years.
174 *
175 * molad The date and time of the mean conjunction of the
176 * sun and moon (new moon). This is the approximate
177 * beginning of a month.
178 *
179 * Rosh Ha-Shanah The first day of the Jewish year (Tishri 1).
180 *
181 * Tishri The first month of the Jewish year.
182 *
183 * ALGORITHMS
184 *
185 * SERIAL DAY NUMBER TO JEWISH DATE
186 *
187 * The simplest approach would be to use the rules stated above to find
188 * the molad of Tishri before and after the given day number. Then use
189 * the molads to find Tishri 1 of the current and following years.
190 * From this the length of the year can be determined and thus the
191 * length of each month. But this method is used as a last resort.
192 *
193 * The first 59 days of the year are the same regardless of the length
194 * of the year. As a result, only the day number of the start of the
195 * year is required.
196 *
197 * Similarly, the last 6 months do not change from year to year. And
198 * since it can be determined whether the year is a leap year by simple
199 * division, the lengths of Adar I and II can be easily calculated. In
200 * fact, all dates after the 3rd month are consistent from year to year
201 * (once it is known whether it is a leap year).
202 *
203 * This means that if the given day number falls in the 3rd month or on
204 * the 30th day of the 2nd month the length of the year must be found,
205 * but in no other case.
206 *
207 * So, the approach used is to take the given day number and round it
208 * to the closest molad of Tishri (first new moon of the year). The
209 * rounding is not really to the *closest* molad, but is such that if
210 * the day number is before the middle of the 3rd month the molad at
211 * the start of the year is found, otherwise the molad at the end of
212 * the year is found.
213 *
214 * Only if the day number is actually found to be in the ambiguous
215 * period of 29 to 31 days is the other molad calculated.
216 *
217 * JEWISH DATE TO SERIAL DAY NUMBER
218 *
219 * The year number is used to find which 19 year metonic cycle contains
220 * the date and which year within the cycle (this is a division and
221 * modulus). This also determines whether it is a leap year.
222 *
223 * If the month is 1 or 2, the calculation is simple addition to the
224 * first of the year.
225 *
226 * If the month is 8 (Nisan) or greater, the calculation is simple
227 * subtraction from beginning of the following year.
228 *
229 * If the month is 4 to 7, it is considered whether it is a leap year
230 * and then simple subtraction from the beginning of the following year
231 * is used.
232 *
233 * Only if it is the 3rd month is both the start and end of the year
234 * required.
235 *
236 * TESTING
237 *
238 * This algorithm has been tested in two ways. First, 510 dates from a
239 * table in "Jewish Calendar Mystery Dispelled" were calculated and
240 * compared to the table. Second, the calculation algorithm described
241 * in "Jewish Calendar Mystery Dispelled" was coded and used to verify
242 * all dates from the year 1 (3761 B.C.) to the year 13760 (10000
243 * A.D.).
244 *
245 * The source code of the verification program is included in this
246 * package.
247 *
248 * REFERENCES
249 *
250 * The Encyclopedia Judaica, the entry for "Calendar"
251 *
252 * The Jewish Encyclopedia
253 *
254 * Jewish Calendar Mystery Dispelled by George Zinberg, Vantage Press,
255 * 1963
256 *
257 * The Comprehensive Hebrew Calendar by Arthur Spier, Behrman House
258 *
259 * The Book of Calendars [note that this work contains many typos]
260 *
261 **************************************************************************/
262
263 #if defined(PHP_WIN32)
264 #pragma setlocale("english")
265 #endif
266
267 #include "sdncal.h"
268
269 #define HALAKIM_PER_HOUR 1080
270 #define HALAKIM_PER_DAY 25920
271 #define HALAKIM_PER_LUNAR_CYCLE ((29 * HALAKIM_PER_DAY) + 13753)
272 #define HALAKIM_PER_METONIC_CYCLE (HALAKIM_PER_LUNAR_CYCLE * (12 * 19 + 7))
273
274 #define JEWISH_SDN_OFFSET 347997
275 #define JEWISH_SDN_MAX 324542846L /* 12/13/887605, greater value raises interger overflow */
276 #define NEW_MOON_OF_CREATION 31524
277
278 #define SUNDAY 0
279 #define MONDAY 1
280 #define TUESDAY 2
281 #define WEDNESDAY 3
282 #define THURSDAY 4
283 #define FRIDAY 5
284 #define SATURDAY 6
285
286 #define NOON (18 * HALAKIM_PER_HOUR)
287 #define AM3_11_20 ((9 * HALAKIM_PER_HOUR) + 204)
288 #define AM9_32_43 ((15 * HALAKIM_PER_HOUR) + 589)
289
290 int monthsPerYear[19] =
291 {
292 12, 12, 13, 12, 12, 13, 12, 13, 12, 12, 13, 12, 12, 13, 12, 12, 13, 12, 13
293 };
294
295 static int yearOffset[19] =
296 {
297 0, 12, 24, 37, 49, 61, 74, 86, 99, 111, 123,
298 136, 148, 160, 173, 185, 197, 210, 222
299 };
300
301 /* names for leap (13-month) year */
302 char *JewishMonthNameLeap[14] =
303 {
304 "",
305 "Tishri",
306 "Heshvan",
307 "Kislev",
308 "Tevet",
309 "Shevat",
310 "Adar I",
311 "Adar II",
312 "Nisan",
313 "Iyyar",
314 "Sivan",
315 "Tammuz",
316 "Av",
317 "Elul"
318 };
319
320 /* names for regular year */
321 char *JewishMonthName[14] =
322 {
323 "",
324 "Tishri",
325 "Heshvan",
326 "Kislev",
327 "Tevet",
328 "Shevat",
329 "",
330 "Adar",
331 "Nisan",
332 "Iyyar",
333 "Sivan",
334 "Tammuz",
335 "Av",
336 "Elul"
337 };
338
339 /* names for leap (13-month) year */
340 char *JewishMonthHebNameLeap[14] =
341 {
342 "",
343 "תשרי",
344 "חשון",
345 "כסלו",
346 "טבת",
347 "שבט",
348 "אדר א'",
349 "אדר ב'",
350 "ניסן",
351 "אייר",
352 "סיון",
353 "תמוז",
354 "אב",
355 "אלול"
356 };
357
358 /* names for regular year */
359 char *JewishMonthHebName[14] =
360 {
361 "",
362 "תשרי",
363 "חשון",
364 "כסלו",
365 "טבת",
366 "שבט",
367 "",
368 "אדר",
369 "ניסן",
370 "אייר",
371 "סיון",
372 "תמוז",
373 "אב",
374 "אלול"
375 };
376
377 /************************************************************************
378 * Given the year within the 19 year metonic cycle and the time of a molad
379 * (new moon) which starts that year, this routine will calculate what day
380 * will be the actual start of the year (Tishri 1 or Rosh Ha-Shanah). This
381 * first day of the year will be the day of the molad unless one of 4 rules
382 * (called dehiyyot) delays it. These 4 rules can delay the start of the
383 * year by as much as 2 days.
384 */
385 static zend_long Tishri1(
386 int metonicYear,
387 zend_long moladDay,
388 zend_long moladHalakim)
389 {
390 zend_long tishri1;
391 int dow;
392 int leapYear;
393 int lastWasLeapYear;
394
395 tishri1 = moladDay;
396 dow = tishri1 % 7;
397 leapYear = metonicYear == 2 || metonicYear == 5 || metonicYear == 7
398 || metonicYear == 10 || metonicYear == 13 || metonicYear == 16
399 || metonicYear == 18;
400 lastWasLeapYear = metonicYear == 3 || metonicYear == 6
401 || metonicYear == 8 || metonicYear == 11 || metonicYear == 14
402 || metonicYear == 17 || metonicYear == 0;
403
404 /* Apply rules 2, 3 and 4. */
405 if ((moladHalakim >= NOON) ||
406 ((!leapYear) && dow == TUESDAY && moladHalakim >= AM3_11_20) ||
407 (lastWasLeapYear && dow == MONDAY && moladHalakim >= AM9_32_43)) {
408 tishri1++;
409 dow++;
410 if (dow == 7) {
411 dow = 0;
412 }
413 }
414 /* Apply rule 1 after the others because it can cause an additional
415 * delay of one day. */
416 if (dow == WEDNESDAY || dow == FRIDAY || dow == SUNDAY) {
417 tishri1++;
418 }
419 return (tishri1);
420 }
421
422 /************************************************************************
423 * Given a metonic cycle number, calculate the date and time of the molad
424 * (new moon) that starts that cycle. Since the length of a metonic cycle
425 * is a constant, this is a simple calculation, except that it requires an
426 * intermediate value which is bigger that 32 bits. Because this
427 * intermediate value only needs 36 to 37 bits and the other numbers are
428 * constants, the process has been reduced to just a few steps.
429 */
430 static void MoladOfMetonicCycle(
431 int metonicCycle,
432 zend_long *pMoladDay,
433 zend_long *pMoladHalakim)
434 {
435 register zend_ulong r1, r2, d1, d2;
436
437 /* Start with the time of the first molad after creation. */
438 r1 = NEW_MOON_OF_CREATION;
439
440 /* Calculate metonicCycle * HALAKIM_PER_METONIC_CYCLE. The upper 32
441 * bits of the result will be in r2 and the lower 16 bits will be
442 * in r1. */
443 r1 += metonicCycle * (HALAKIM_PER_METONIC_CYCLE & 0xFFFF);
444 r2 = r1 >> 16;
445 r2 += metonicCycle * ((HALAKIM_PER_METONIC_CYCLE >> 16) & 0xFFFF);
446
447 /* Calculate r2r1 / HALAKIM_PER_DAY. The remainder will be in r1, the
448 * upper 16 bits of the quotient will be in d2 and the lower 16 bits
449 * will be in d1. */
450 d2 = r2 / HALAKIM_PER_DAY;
451 r2 -= d2 * HALAKIM_PER_DAY;
452 r1 = (r2 << 16) | (r1 & 0xFFFF);
453 d1 = r1 / HALAKIM_PER_DAY;
454 r1 -= d1 * HALAKIM_PER_DAY;
455
456 *pMoladDay = (d2 << 16) | d1;
457 *pMoladHalakim = r1;
458 }
459
460 /************************************************************************
461 * Given a day number, find the molad of Tishri (the new moon at the start
462 * of a year) which is closest to that day number. It's not really the
463 * *closest* molad that we want here. If the input day is in the first two
464 * months, we want the molad at the start of the year. If the input day is
465 * in the fourth to last months, we want the molad at the end of the year.
466 * If the input day is in the third month, it doesn't matter which molad is
467 * returned, because both will be required. This type of "rounding" allows
468 * us to avoid calculating the length of the year in most cases.
469 */
470 static void FindTishriMolad(
471 zend_long inputDay,
472 int *pMetonicCycle,
473 int *pMetonicYear,
474 zend_long *pMoladDay,
475 zend_long *pMoladHalakim)
476 {
477 zend_long moladDay;
478 zend_long moladHalakim;
479 int metonicCycle;
480 int metonicYear;
481
482 /* Estimate the metonic cycle number. Note that this may be an under
483 * estimate because there are 6939.6896 days in a metonic cycle not
484 * 6940, but it will never be an over estimate. The loop below will
485 * correct for any error in this estimate. */
486 metonicCycle = (inputDay + 310) / 6940;
487
488 /* Calculate the time of the starting molad for this metonic cycle. */
489 MoladOfMetonicCycle(metonicCycle, &moladDay, &moladHalakim);
490
491 /* If the above was an under estimate, increment the cycle number until
492 * the correct one is found. For modern dates this loop is about 98.6%
493 * likely to not execute, even once, because the above estimate is
494 * really quite close. */
495 while (moladDay < inputDay - 6940 + 310) {
496 metonicCycle++;
497 moladHalakim += HALAKIM_PER_METONIC_CYCLE;
498 moladDay += moladHalakim / HALAKIM_PER_DAY;
499 moladHalakim = moladHalakim % HALAKIM_PER_DAY;
500 }
501
502 /* Find the molad of Tishri closest to this date. */
503 for (metonicYear = 0; metonicYear < 18; metonicYear++) {
504 if (moladDay > inputDay - 74) {
505 break;
506 }
507 moladHalakim += HALAKIM_PER_LUNAR_CYCLE * monthsPerYear[metonicYear];
508 moladDay += moladHalakim / HALAKIM_PER_DAY;
509 moladHalakim = moladHalakim % HALAKIM_PER_DAY;
510 }
511
512 *pMetonicCycle = metonicCycle;
513 *pMetonicYear = metonicYear;
514 *pMoladDay = moladDay;
515 *pMoladHalakim = moladHalakim;
516 }
517
518 /************************************************************************
519 * Given a year, find the number of the first day of that year and the date
520 * and time of the starting molad.
521 */
522 static void FindStartOfYear(
523 int year,
524 int *pMetonicCycle,
525 int *pMetonicYear,
526 zend_long *pMoladDay,
527 zend_long *pMoladHalakim,
528 int *pTishri1)
529 {
530 *pMetonicCycle = (year - 1) / 19;
531 *pMetonicYear = (year - 1) % 19;
532 MoladOfMetonicCycle(*pMetonicCycle, pMoladDay, pMoladHalakim);
533
534 *pMoladHalakim += HALAKIM_PER_LUNAR_CYCLE * yearOffset[*pMetonicYear];
535 *pMoladDay += *pMoladHalakim / HALAKIM_PER_DAY;
536 *pMoladHalakim = *pMoladHalakim % HALAKIM_PER_DAY;
537
538 *pTishri1 = Tishri1(*pMetonicYear, *pMoladDay, *pMoladHalakim);
539 }
540
541 /************************************************************************
542 * Given a serial day number (SDN), find the corresponding year, month and
543 * day in the Jewish calendar. The three output values will always be
544 * modified. If the input SDN is before the first day of year 1, they will
545 * all be set to zero, otherwise *pYear will be > 0; *pMonth will be in the
546 * range 1 to 13 inclusive; *pDay will be in the range 1 to 30 inclusive.
547 */
548 void SdnToJewish(
549 zend_long sdn,
550 int *pYear,
551 int *pMonth,
552 int *pDay)
553 {
554 zend_long inputDay;
555 zend_long day;
556 zend_long halakim;
557 int metonicCycle;
558 int metonicYear;
559 int tishri1;
560 int tishri1After;
561 int yearLength;
562
563 if (sdn <= JEWISH_SDN_OFFSET || sdn > JEWISH_SDN_MAX) {
564 *pYear = 0;
565 *pMonth = 0;
566 *pDay = 0;
567 return;
568 }
569 inputDay = sdn - JEWISH_SDN_OFFSET;
570
571 FindTishriMolad(inputDay, &metonicCycle, &metonicYear, &day, &halakim);
572 tishri1 = Tishri1(metonicYear, day, halakim);
573
574 if (inputDay >= tishri1) {
575 /* It found Tishri 1 at the start of the year. */
576 *pYear = metonicCycle * 19 + metonicYear + 1;
577 if (inputDay < tishri1 + 59) {
578 if (inputDay < tishri1 + 30) {
579 *pMonth = 1;
580 *pDay = inputDay - tishri1 + 1;
581 } else {
582 *pMonth = 2;
583 *pDay = inputDay - tishri1 - 29;
584 }
585 return;
586 }
587 /* We need the length of the year to figure this out, so find
588 * Tishri 1 of the next year. */
589 halakim += HALAKIM_PER_LUNAR_CYCLE * monthsPerYear[metonicYear];
590 day += halakim / HALAKIM_PER_DAY;
591 halakim = halakim % HALAKIM_PER_DAY;
592 tishri1After = Tishri1((metonicYear + 1) % 19, day, halakim);
593 } else {
594 /* It found Tishri 1 at the end of the year. */
595 *pYear = metonicCycle * 19 + metonicYear;
596 if (inputDay >= tishri1 - 177) {
597 /* It is one of the last 6 months of the year. */
598 if (inputDay > tishri1 - 30) {
599 *pMonth = 13;
600 *pDay = inputDay - tishri1 + 30;
601 } else if (inputDay > tishri1 - 60) {
602 *pMonth = 12;
603 *pDay = inputDay - tishri1 + 60;
604 } else if (inputDay > tishri1 - 89) {
605 *pMonth = 11;
606 *pDay = inputDay - tishri1 + 89;
607 } else if (inputDay > tishri1 - 119) {
608 *pMonth = 10;
609 *pDay = inputDay - tishri1 + 119;
610 } else if (inputDay > tishri1 - 148) {
611 *pMonth = 9;
612 *pDay = inputDay - tishri1 + 148;
613 } else {
614 *pMonth = 8;
615 *pDay = inputDay - tishri1 + 178;
616 }
617 return;
618 } else {
619 if (monthsPerYear[(*pYear - 1) % 19] == 13) {
620 *pMonth = 7;
621 *pDay = inputDay - tishri1 + 207;
622 if (*pDay > 0)
623 return;
624 (*pMonth)--;
625 (*pDay) += 30;
626 if (*pDay > 0)
627 return;
628 (*pMonth)--;
629 (*pDay) += 30;
630 } else {
631 *pMonth = 7;
632 *pDay = inputDay - tishri1 + 207;
633 if (*pDay > 0)
634 return;
635 (*pMonth) -= 2;
636 (*pDay) += 30;
637 }
638 if (*pDay > 0)
639 return;
640 (*pMonth)--;
641 (*pDay) += 29;
642 if (*pDay > 0)
643 return;
644
645 /* We need the length of the year to figure this out, so find
646 * Tishri 1 of this year. */
647 tishri1After = tishri1;
648 FindTishriMolad(day - 365,
649 &metonicCycle, &metonicYear, &day, &halakim);
650 tishri1 = Tishri1(metonicYear, day, halakim);
651 }
652 }
653
654 yearLength = tishri1After - tishri1;
655 day = inputDay - tishri1 - 29;
656 if (yearLength == 355 || yearLength == 385) {
657 /* Heshvan has 30 days */
658 if (day <= 30) {
659 *pMonth = 2;
660 *pDay = day;
661 return;
662 }
663 day -= 30;
664 } else {
665 /* Heshvan has 29 days */
666 if (day <= 29) {
667 *pMonth = 2;
668 *pDay = day;
669 return;
670 }
671 day -= 29;
672 }
673
674 /* It has to be Kislev. */
675 *pMonth = 3;
676 *pDay = day;
677 }
678
679 /************************************************************************
680 * Given a year, month and day in the Jewish calendar, find the
681 * corresponding serial day number (SDN). Zero is returned when the input
682 * date is detected as invalid. The return value will be > 0 for all valid
683 * dates, but there are some invalid dates that will return a positive
684 * value. To verify that a date is valid, convert it to SDN and then back
685 * and compare with the original.
686 */
687 zend_long JewishToSdn(
688 int year,
689 int month,
690 int day)
691 {
692 zend_long sdn;
693 int metonicCycle;
694 int metonicYear;
695 int tishri1;
696 int tishri1After;
697 zend_long moladDay;
698 zend_long moladHalakim;
699 int yearLength;
700 int lengthOfAdarIAndII;
701
702 if (year <= 0 || day <= 0 || day > 30) {
703 return (0);
704 }
705 switch (month) {
706 case 1:
707 case 2:
708 /* It is Tishri or Heshvan - don't need the year length. */
709 FindStartOfYear(year, &metonicCycle, &metonicYear,
710 &moladDay, &moladHalakim, &tishri1);
711 if (month == 1) {
712 sdn = tishri1 + day - 1;
713 } else {
714 sdn = tishri1 + day + 29;
715 }
716 break;
717
718 case 3:
719 /* It is Kislev - must find the year length. */
720
721 /* Find the start of the year. */
722 FindStartOfYear(year, &metonicCycle, &metonicYear,
723 &moladDay, &moladHalakim, &tishri1);
724
725 /* Find the end of the year. */
726 moladHalakim += HALAKIM_PER_LUNAR_CYCLE * monthsPerYear[metonicYear];
727 moladDay += moladHalakim / HALAKIM_PER_DAY;
728 moladHalakim = moladHalakim % HALAKIM_PER_DAY;
729 tishri1After = Tishri1((metonicYear + 1) % 19, moladDay, moladHalakim);
730
731 yearLength = tishri1After - tishri1;
732
733 if (yearLength == 355 || yearLength == 385) {
734 sdn = tishri1 + day + 59;
735 } else {
736 sdn = tishri1 + day + 58;
737 }
738 break;
739
740 case 4:
741 case 5:
742 case 6:
743 /* It is Tevet, Shevat or Adar I - don't need the year length. */
744
745 FindStartOfYear(year + 1, &metonicCycle, &metonicYear,
746 &moladDay, &moladHalakim, &tishri1After);
747
748 if (monthsPerYear[(year - 1) % 19] == 12) {
749 lengthOfAdarIAndII = 29;
750 } else {
751 lengthOfAdarIAndII = 59;
752 }
753
754 if (month == 4) {
755 sdn = tishri1After + day - lengthOfAdarIAndII - 237;
756 } else if (month == 5) {
757 sdn = tishri1After + day - lengthOfAdarIAndII - 208;
758 } else {
759 sdn = tishri1After + day - lengthOfAdarIAndII - 178;
760 }
761 break;
762
763 default:
764 /* It is Adar II or later - don't need the year length. */
765 FindStartOfYear(year + 1, &metonicCycle, &metonicYear,
766 &moladDay, &moladHalakim, &tishri1After);
767
768 switch (month) {
769 case 7:
770 sdn = tishri1After + day - 207;
771 break;
772 case 8:
773 sdn = tishri1After + day - 178;
774 break;
775 case 9:
776 sdn = tishri1After + day - 148;
777 break;
778 case 10:
779 sdn = tishri1After + day - 119;
780 break;
781 case 11:
782 sdn = tishri1After + day - 89;
783 break;
784 case 12:
785 sdn = tishri1After + day - 60;
786 break;
787 case 13:
788 sdn = tishri1After + day - 30;
789 break;
790 default:
791 return (0);
792 }
793 }
794 return (sdn + JEWISH_SDN_OFFSET);
795 }
796
797 /*
798 * Local variables:
799 * tab-width: 4
800 * c-basic-offset: 4
801 * End:
802 * vim600: sw=4 ts=4 fdm=marker
803 * vim<600: sw=4 ts=4
804 */