Add --date={local,relative,default}
[git/git.git] / date.c
1 /*
2 * GIT - The information manager from hell
3 *
4 * Copyright (C) Linus Torvalds, 2005
5 */
6
7 #include "cache.h"
8
9 static time_t my_mktime(struct tm *tm)
10 {
11 static const int mdays[] = {
12 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
13 };
14 int year = tm->tm_year - 70;
15 int month = tm->tm_mon;
16 int day = tm->tm_mday;
17
18 if (year < 0 || year > 129) /* algo only works for 1970-2099 */
19 return -1;
20 if (month < 0 || month > 11) /* array bounds */
21 return -1;
22 if (month < 2 || (year + 2) % 4)
23 day--;
24 return (year * 365 + (year + 1) / 4 + mdays[month] + day) * 24*60*60UL +
25 tm->tm_hour * 60*60 + tm->tm_min * 60 + tm->tm_sec;
26 }
27
28 static const char *month_names[] = {
29 "January", "February", "March", "April", "May", "June",
30 "July", "August", "September", "October", "November", "December"
31 };
32
33 static const char *weekday_names[] = {
34 "Sundays", "Mondays", "Tuesdays", "Wednesdays", "Thursdays", "Fridays", "Saturdays"
35 };
36
37 static time_t gm_time_t(unsigned long time, int tz)
38 {
39 int minutes;
40
41 minutes = tz < 0 ? -tz : tz;
42 minutes = (minutes / 100)*60 + (minutes % 100);
43 minutes = tz < 0 ? -minutes : minutes;
44 return time + minutes * 60;
45 }
46
47 /*
48 * The "tz" thing is passed in as this strange "decimal parse of tz"
49 * thing, which means that tz -0100 is passed in as the integer -100,
50 * even though it means "sixty minutes off"
51 */
52 static struct tm *time_to_tm(unsigned long time, int tz)
53 {
54 time_t t = gm_time_t(time, tz);
55 return gmtime(&t);
56 }
57
58 /*
59 * What value of "tz" was in effect back then at "time" in the
60 * local timezone?
61 */
62 static int local_tzoffset(unsigned long time)
63 {
64 time_t t, t_local;
65 struct tm tm;
66 int offset, eastwest;
67
68 t = time;
69 localtime_r(&t, &tm);
70 t_local = my_mktime(&tm);
71
72 if (t_local < t) {
73 eastwest = -1;
74 offset = t - t_local;
75 } else {
76 eastwest = 1;
77 offset = t_local - t;
78 }
79 offset /= 60; /* in minutes */
80 offset = (offset % 60) + ((offset / 60) * 100);
81 return offset * eastwest;
82 }
83
84 const char *show_date(unsigned long time, int tz, enum date_mode mode)
85 {
86 struct tm *tm;
87 static char timebuf[200];
88
89 if (mode == DATE_RELATIVE) {
90 unsigned long diff;
91 struct timeval now;
92 gettimeofday(&now, NULL);
93 if (now.tv_sec < time)
94 return "in the future";
95 diff = now.tv_sec - time;
96 if (diff < 90) {
97 snprintf(timebuf, sizeof(timebuf), "%lu seconds ago", diff);
98 return timebuf;
99 }
100 /* Turn it into minutes */
101 diff = (diff + 30) / 60;
102 if (diff < 90) {
103 snprintf(timebuf, sizeof(timebuf), "%lu minutes ago", diff);
104 return timebuf;
105 }
106 /* Turn it into hours */
107 diff = (diff + 30) / 60;
108 if (diff < 36) {
109 snprintf(timebuf, sizeof(timebuf), "%lu hours ago", diff);
110 return timebuf;
111 }
112 /* We deal with number of days from here on */
113 diff = (diff + 12) / 24;
114 if (diff < 14) {
115 snprintf(timebuf, sizeof(timebuf), "%lu days ago", diff);
116 return timebuf;
117 }
118 /* Say weeks for the past 10 weeks or so */
119 if (diff < 70) {
120 snprintf(timebuf, sizeof(timebuf), "%lu weeks ago", (diff + 3) / 7);
121 return timebuf;
122 }
123 /* Say months for the past 12 months or so */
124 if (diff < 360) {
125 snprintf(timebuf, sizeof(timebuf), "%lu months ago", (diff + 15) / 30);
126 return timebuf;
127 }
128 /* Else fall back on absolute format.. */
129 }
130
131 if (mode == DATE_LOCAL)
132 tz = local_tzoffset(time);
133
134 tm = time_to_tm(time, tz);
135 if (!tm)
136 return NULL;
137 if (mode == DATE_SHORT)
138 sprintf(timebuf, "%04d-%02d-%02d", tm->tm_year + 1900,
139 tm->tm_mon + 1, tm->tm_mday);
140 else
141 sprintf(timebuf, "%.3s %.3s %d %02d:%02d:%02d %d%c%+05d",
142 weekday_names[tm->tm_wday],
143 month_names[tm->tm_mon],
144 tm->tm_mday,
145 tm->tm_hour, tm->tm_min, tm->tm_sec,
146 tm->tm_year + 1900,
147 (mode == DATE_LOCAL) ? 0 : ' ',
148 tz);
149 return timebuf;
150 }
151
152 const char *show_rfc2822_date(unsigned long time, int tz)
153 {
154 struct tm *tm;
155 static char timebuf[200];
156
157 tm = time_to_tm(time, tz);
158 if (!tm)
159 return NULL;
160 sprintf(timebuf, "%.3s, %d %.3s %d %02d:%02d:%02d %+05d",
161 weekday_names[tm->tm_wday], tm->tm_mday,
162 month_names[tm->tm_mon], tm->tm_year + 1900,
163 tm->tm_hour, tm->tm_min, tm->tm_sec, tz);
164 return timebuf;
165 }
166
167 /*
168 * Check these. And note how it doesn't do the summer-time conversion.
169 *
170 * In my world, it's always summer, and things are probably a bit off
171 * in other ways too.
172 */
173 static const struct {
174 const char *name;
175 int offset;
176 int dst;
177 } timezone_names[] = {
178 { "IDLW", -12, 0, }, /* International Date Line West */
179 { "NT", -11, 0, }, /* Nome */
180 { "CAT", -10, 0, }, /* Central Alaska */
181 { "HST", -10, 0, }, /* Hawaii Standard */
182 { "HDT", -10, 1, }, /* Hawaii Daylight */
183 { "YST", -9, 0, }, /* Yukon Standard */
184 { "YDT", -9, 1, }, /* Yukon Daylight */
185 { "PST", -8, 0, }, /* Pacific Standard */
186 { "PDT", -8, 1, }, /* Pacific Daylight */
187 { "MST", -7, 0, }, /* Mountain Standard */
188 { "MDT", -7, 1, }, /* Mountain Daylight */
189 { "CST", -6, 0, }, /* Central Standard */
190 { "CDT", -6, 1, }, /* Central Daylight */
191 { "EST", -5, 0, }, /* Eastern Standard */
192 { "EDT", -5, 1, }, /* Eastern Daylight */
193 { "AST", -3, 0, }, /* Atlantic Standard */
194 { "ADT", -3, 1, }, /* Atlantic Daylight */
195 { "WAT", -1, 0, }, /* West Africa */
196
197 { "GMT", 0, 0, }, /* Greenwich Mean */
198 { "UTC", 0, 0, }, /* Universal (Coordinated) */
199
200 { "WET", 0, 0, }, /* Western European */
201 { "BST", 0, 1, }, /* British Summer */
202 { "CET", +1, 0, }, /* Central European */
203 { "MET", +1, 0, }, /* Middle European */
204 { "MEWT", +1, 0, }, /* Middle European Winter */
205 { "MEST", +1, 1, }, /* Middle European Summer */
206 { "CEST", +1, 1, }, /* Central European Summer */
207 { "MESZ", +1, 1, }, /* Middle European Summer */
208 { "FWT", +1, 0, }, /* French Winter */
209 { "FST", +1, 1, }, /* French Summer */
210 { "EET", +2, 0, }, /* Eastern Europe, USSR Zone 1 */
211 { "EEST", +2, 1, }, /* Eastern European Daylight */
212 { "WAST", +7, 0, }, /* West Australian Standard */
213 { "WADT", +7, 1, }, /* West Australian Daylight */
214 { "CCT", +8, 0, }, /* China Coast, USSR Zone 7 */
215 { "JST", +9, 0, }, /* Japan Standard, USSR Zone 8 */
216 { "EAST", +10, 0, }, /* Eastern Australian Standard */
217 { "EADT", +10, 1, }, /* Eastern Australian Daylight */
218 { "GST", +10, 0, }, /* Guam Standard, USSR Zone 9 */
219 { "NZT", +11, 0, }, /* New Zealand */
220 { "NZST", +11, 0, }, /* New Zealand Standard */
221 { "NZDT", +11, 1, }, /* New Zealand Daylight */
222 { "IDLE", +12, 0, }, /* International Date Line East */
223 };
224
225 static int match_string(const char *date, const char *str)
226 {
227 int i = 0;
228
229 for (i = 0; *date; date++, str++, i++) {
230 if (*date == *str)
231 continue;
232 if (toupper(*date) == toupper(*str))
233 continue;
234 if (!isalnum(*date))
235 break;
236 return 0;
237 }
238 return i;
239 }
240
241 static int skip_alpha(const char *date)
242 {
243 int i = 0;
244 do {
245 i++;
246 } while (isalpha(date[i]));
247 return i;
248 }
249
250 /*
251 * Parse month, weekday, or timezone name
252 */
253 static int match_alpha(const char *date, struct tm *tm, int *offset)
254 {
255 int i;
256
257 for (i = 0; i < 12; i++) {
258 int match = match_string(date, month_names[i]);
259 if (match >= 3) {
260 tm->tm_mon = i;
261 return match;
262 }
263 }
264
265 for (i = 0; i < 7; i++) {
266 int match = match_string(date, weekday_names[i]);
267 if (match >= 3) {
268 tm->tm_wday = i;
269 return match;
270 }
271 }
272
273 for (i = 0; i < ARRAY_SIZE(timezone_names); i++) {
274 int match = match_string(date, timezone_names[i].name);
275 if (match >= 3) {
276 int off = timezone_names[i].offset;
277
278 /* This is bogus, but we like summer */
279 off += timezone_names[i].dst;
280
281 /* Only use the tz name offset if we don't have anything better */
282 if (*offset == -1)
283 *offset = 60*off;
284
285 return match;
286 }
287 }
288
289 if (match_string(date, "PM") == 2) {
290 tm->tm_hour = (tm->tm_hour % 12) + 12;
291 return 2;
292 }
293
294 if (match_string(date, "AM") == 2) {
295 tm->tm_hour = (tm->tm_hour % 12) + 0;
296 return 2;
297 }
298
299 /* BAD CRAP */
300 return skip_alpha(date);
301 }
302
303 static int is_date(int year, int month, int day, struct tm *now_tm, time_t now, struct tm *tm)
304 {
305 if (month > 0 && month < 13 && day > 0 && day < 32) {
306 struct tm check = *tm;
307 struct tm *r = (now_tm ? &check : tm);
308 time_t specified;
309
310 r->tm_mon = month - 1;
311 r->tm_mday = day;
312 if (year == -1) {
313 if (!now_tm)
314 return 1;
315 r->tm_year = now_tm->tm_year;
316 }
317 else if (year >= 1970 && year < 2100)
318 r->tm_year = year - 1900;
319 else if (year > 70 && year < 100)
320 r->tm_year = year;
321 else if (year < 38)
322 r->tm_year = year + 100;
323 else
324 return 0;
325 if (!now_tm)
326 return 1;
327
328 specified = my_mktime(r);
329
330 /* Be it commit time or author time, it does not make
331 * sense to specify timestamp way into the future. Make
332 * sure it is not later than ten days from now...
333 */
334 if (now + 10*24*3600 < specified)
335 return 0;
336 tm->tm_mon = r->tm_mon;
337 tm->tm_mday = r->tm_mday;
338 if (year != -1)
339 tm->tm_year = r->tm_year;
340 return 1;
341 }
342 return 0;
343 }
344
345 static int match_multi_number(unsigned long num, char c, const char *date, char *end, struct tm *tm)
346 {
347 time_t now;
348 struct tm now_tm;
349 struct tm *refuse_future;
350 long num2, num3;
351
352 num2 = strtol(end+1, &end, 10);
353 num3 = -1;
354 if (*end == c && isdigit(end[1]))
355 num3 = strtol(end+1, &end, 10);
356
357 /* Time? Date? */
358 switch (c) {
359 case ':':
360 if (num3 < 0)
361 num3 = 0;
362 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
363 tm->tm_hour = num;
364 tm->tm_min = num2;
365 tm->tm_sec = num3;
366 break;
367 }
368 return 0;
369
370 case '-':
371 case '/':
372 case '.':
373 now = time(NULL);
374 refuse_future = NULL;
375 if (gmtime_r(&now, &now_tm))
376 refuse_future = &now_tm;
377
378 if (num > 70) {
379 /* yyyy-mm-dd? */
380 if (is_date(num, num2, num3, refuse_future, now, tm))
381 break;
382 /* yyyy-dd-mm? */
383 if (is_date(num, num3, num2, refuse_future, now, tm))
384 break;
385 }
386 /* Our eastern European friends say dd.mm.yy[yy]
387 * is the norm there, so giving precedence to
388 * mm/dd/yy[yy] form only when separator is not '.'
389 */
390 if (c != '.' &&
391 is_date(num3, num, num2, refuse_future, now, tm))
392 break;
393 /* European dd.mm.yy[yy] or funny US dd/mm/yy[yy] */
394 if (is_date(num3, num2, num, refuse_future, now, tm))
395 break;
396 /* Funny European mm.dd.yy */
397 if (c == '.' &&
398 is_date(num3, num, num2, refuse_future, now, tm))
399 break;
400 return 0;
401 }
402 return end - date;
403 }
404
405 /*
406 * We've seen a digit. Time? Year? Date?
407 */
408 static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt)
409 {
410 int n;
411 char *end;
412 unsigned long num;
413
414 num = strtoul(date, &end, 10);
415
416 /*
417 * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
418 */
419 if (num > 946684800) {
420 time_t time = num;
421 if (gmtime_r(&time, tm)) {
422 *tm_gmt = 1;
423 return end - date;
424 }
425 }
426
427 /*
428 * Check for special formats: num[-.:/]num[same]num
429 */
430 switch (*end) {
431 case ':':
432 case '.':
433 case '/':
434 case '-':
435 if (isdigit(end[1])) {
436 int match = match_multi_number(num, *end, date, end, tm);
437 if (match)
438 return match;
439 }
440 }
441
442 /*
443 * None of the special formats? Try to guess what
444 * the number meant. We use the number of digits
445 * to make a more educated guess..
446 */
447 n = 0;
448 do {
449 n++;
450 } while (isdigit(date[n]));
451
452 /* Four-digit year or a timezone? */
453 if (n == 4) {
454 if (num <= 1400 && *offset == -1) {
455 unsigned int minutes = num % 100;
456 unsigned int hours = num / 100;
457 *offset = hours*60 + minutes;
458 } else if (num > 1900 && num < 2100)
459 tm->tm_year = num - 1900;
460 return n;
461 }
462
463 /*
464 * NOTE! We will give precedence to day-of-month over month or
465 * year numbers in the 1-12 range. So 05 is always "mday 5",
466 * unless we already have a mday..
467 *
468 * IOW, 01 Apr 05 parses as "April 1st, 2005".
469 */
470 if (num > 0 && num < 32 && tm->tm_mday < 0) {
471 tm->tm_mday = num;
472 return n;
473 }
474
475 /* Two-digit year? */
476 if (n == 2 && tm->tm_year < 0) {
477 if (num < 10 && tm->tm_mday >= 0) {
478 tm->tm_year = num + 100;
479 return n;
480 }
481 if (num >= 70) {
482 tm->tm_year = num;
483 return n;
484 }
485 }
486
487 if (num > 0 && num < 32) {
488 tm->tm_mday = num;
489 } else if (num > 1900) {
490 tm->tm_year = num - 1900;
491 } else if (num > 70) {
492 tm->tm_year = num;
493 } else if (num > 0 && num < 13) {
494 tm->tm_mon = num-1;
495 }
496
497 return n;
498 }
499
500 static int match_tz(const char *date, int *offp)
501 {
502 char *end;
503 int offset = strtoul(date+1, &end, 10);
504 int min, hour;
505 int n = end - date - 1;
506
507 min = offset % 100;
508 hour = offset / 100;
509
510 /*
511 * Don't accept any random crap.. At least 3 digits, and
512 * a valid minute. We might want to check that the minutes
513 * are divisible by 30 or something too.
514 */
515 if (min < 60 && n > 2) {
516 offset = hour*60+min;
517 if (*date == '-')
518 offset = -offset;
519
520 *offp = offset;
521 }
522 return end - date;
523 }
524
525 static int date_string(unsigned long date, int offset, char *buf, int len)
526 {
527 int sign = '+';
528
529 if (offset < 0) {
530 offset = -offset;
531 sign = '-';
532 }
533 return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
534 }
535
536 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
537 (i.e. English) day/month names, and it doesn't work correctly with %z. */
538 int parse_date(const char *date, char *result, int maxlen)
539 {
540 struct tm tm;
541 int offset, tm_gmt;
542 time_t then;
543
544 memset(&tm, 0, sizeof(tm));
545 tm.tm_year = -1;
546 tm.tm_mon = -1;
547 tm.tm_mday = -1;
548 tm.tm_isdst = -1;
549 offset = -1;
550 tm_gmt = 0;
551
552 for (;;) {
553 int match = 0;
554 unsigned char c = *date;
555
556 /* Stop at end of string or newline */
557 if (!c || c == '\n')
558 break;
559
560 if (isalpha(c))
561 match = match_alpha(date, &tm, &offset);
562 else if (isdigit(c))
563 match = match_digit(date, &tm, &offset, &tm_gmt);
564 else if ((c == '-' || c == '+') && isdigit(date[1]))
565 match = match_tz(date, &offset);
566
567 if (!match) {
568 /* BAD CRAP */
569 match = 1;
570 }
571
572 date += match;
573 }
574
575 /* mktime uses local timezone */
576 then = my_mktime(&tm);
577 if (offset == -1)
578 offset = (then - mktime(&tm)) / 60;
579
580 if (then == -1)
581 return -1;
582
583 if (!tm_gmt)
584 then -= offset * 60;
585 return date_string(then, offset, result, maxlen);
586 }
587
588 void datestamp(char *buf, int bufsize)
589 {
590 time_t now;
591 int offset;
592
593 time(&now);
594
595 offset = my_mktime(localtime(&now)) - now;
596 offset /= 60;
597
598 date_string(now, offset, buf, bufsize);
599 }
600
601 static void update_tm(struct tm *tm, unsigned long sec)
602 {
603 time_t n = mktime(tm) - sec;
604 localtime_r(&n, tm);
605 }
606
607 static void date_yesterday(struct tm *tm, int *num)
608 {
609 update_tm(tm, 24*60*60);
610 }
611
612 static void date_time(struct tm *tm, int hour)
613 {
614 if (tm->tm_hour < hour)
615 date_yesterday(tm, NULL);
616 tm->tm_hour = hour;
617 tm->tm_min = 0;
618 tm->tm_sec = 0;
619 }
620
621 static void date_midnight(struct tm *tm, int *num)
622 {
623 date_time(tm, 0);
624 }
625
626 static void date_noon(struct tm *tm, int *num)
627 {
628 date_time(tm, 12);
629 }
630
631 static void date_tea(struct tm *tm, int *num)
632 {
633 date_time(tm, 17);
634 }
635
636 static void date_pm(struct tm *tm, int *num)
637 {
638 int hour, n = *num;
639 *num = 0;
640
641 hour = tm->tm_hour;
642 if (n) {
643 hour = n;
644 tm->tm_min = 0;
645 tm->tm_sec = 0;
646 }
647 tm->tm_hour = (hour % 12) + 12;
648 }
649
650 static void date_am(struct tm *tm, int *num)
651 {
652 int hour, n = *num;
653 *num = 0;
654
655 hour = tm->tm_hour;
656 if (n) {
657 hour = n;
658 tm->tm_min = 0;
659 tm->tm_sec = 0;
660 }
661 tm->tm_hour = (hour % 12);
662 }
663
664 static const struct special {
665 const char *name;
666 void (*fn)(struct tm *, int *);
667 } special[] = {
668 { "yesterday", date_yesterday },
669 { "noon", date_noon },
670 { "midnight", date_midnight },
671 { "tea", date_tea },
672 { "PM", date_pm },
673 { "AM", date_am },
674 { NULL }
675 };
676
677 static const char *number_name[] = {
678 "zero", "one", "two", "three", "four",
679 "five", "six", "seven", "eight", "nine", "ten",
680 };
681
682 static const struct typelen {
683 const char *type;
684 int length;
685 } typelen[] = {
686 { "seconds", 1 },
687 { "minutes", 60 },
688 { "hours", 60*60 },
689 { "days", 24*60*60 },
690 { "weeks", 7*24*60*60 },
691 { NULL }
692 };
693
694 static const char *approxidate_alpha(const char *date, struct tm *tm, int *num)
695 {
696 const struct typelen *tl;
697 const struct special *s;
698 const char *end = date;
699 int i;
700
701 while (isalpha(*++end));
702 ;
703
704 for (i = 0; i < 12; i++) {
705 int match = match_string(date, month_names[i]);
706 if (match >= 3) {
707 tm->tm_mon = i;
708 return end;
709 }
710 }
711
712 for (s = special; s->name; s++) {
713 int len = strlen(s->name);
714 if (match_string(date, s->name) == len) {
715 s->fn(tm, num);
716 return end;
717 }
718 }
719
720 if (!*num) {
721 for (i = 1; i < 11; i++) {
722 int len = strlen(number_name[i]);
723 if (match_string(date, number_name[i]) == len) {
724 *num = i;
725 return end;
726 }
727 }
728 if (match_string(date, "last") == 4)
729 *num = 1;
730 return end;
731 }
732
733 tl = typelen;
734 while (tl->type) {
735 int len = strlen(tl->type);
736 if (match_string(date, tl->type) >= len-1) {
737 update_tm(tm, tl->length * *num);
738 *num = 0;
739 return end;
740 }
741 tl++;
742 }
743
744 for (i = 0; i < 7; i++) {
745 int match = match_string(date, weekday_names[i]);
746 if (match >= 3) {
747 int diff, n = *num -1;
748 *num = 0;
749
750 diff = tm->tm_wday - i;
751 if (diff <= 0)
752 n++;
753 diff += 7*n;
754
755 update_tm(tm, diff * 24 * 60 * 60);
756 return end;
757 }
758 }
759
760 if (match_string(date, "months") >= 5) {
761 int n = tm->tm_mon - *num;
762 *num = 0;
763 while (n < 0) {
764 n += 12;
765 tm->tm_year--;
766 }
767 tm->tm_mon = n;
768 return end;
769 }
770
771 if (match_string(date, "years") >= 4) {
772 tm->tm_year -= *num;
773 *num = 0;
774 return end;
775 }
776
777 return end;
778 }
779
780 static const char *approxidate_digit(const char *date, struct tm *tm, int *num)
781 {
782 char *end;
783 unsigned long number = strtoul(date, &end, 10);
784
785 switch (*end) {
786 case ':':
787 case '.':
788 case '/':
789 case '-':
790 if (isdigit(end[1])) {
791 int match = match_multi_number(number, *end, date, end, tm);
792 if (match)
793 return date + match;
794 }
795 }
796
797 *num = number;
798 return end;
799 }
800
801 unsigned long approxidate(const char *date)
802 {
803 int number = 0;
804 struct tm tm, now;
805 struct timeval tv;
806 char buffer[50];
807
808 if (parse_date(date, buffer, sizeof(buffer)) > 0)
809 return strtoul(buffer, NULL, 10);
810
811 gettimeofday(&tv, NULL);
812 localtime_r(&tv.tv_sec, &tm);
813 now = tm;
814 for (;;) {
815 unsigned char c = *date;
816 if (!c)
817 break;
818 date++;
819 if (isdigit(c)) {
820 date = approxidate_digit(date-1, &tm, &number);
821 continue;
822 }
823 if (isalpha(c))
824 date = approxidate_alpha(date-1, &tm, &number);
825 }
826 if (number > 0 && number < 32)
827 tm.tm_mday = number;
828 if (tm.tm_mon > now.tm_mon && tm.tm_year == now.tm_year)
829 tm.tm_year--;
830 return mktime(&tm);
831 }