xref: /netbsd-src/lib/libc/time/zdump.c (revision 82ad575716605df31379cf04a2f3efbc97b8a6f5)
1 /*	$NetBSD: zdump.c,v 1.26 2012/10/24 00:10:03 christos Exp $	*/
2 /*
3 ** This file is in the public domain, so clarified as of
4 ** 2009-05-17 by Arthur David Olson.
5 */
6 
7 #include <sys/cdefs.h>
8 #ifndef lint
9 __RCSID("$NetBSD: zdump.c,v 1.26 2012/10/24 00:10:03 christos Exp $");
10 #endif /* !defined lint */
11 
12 #include "version.h"
13 /*
14 ** This code has been made independent of the rest of the time
15 ** conversion package to increase confidence in the verification it provides.
16 ** You can use this code to help in verifying other implementations.
17 */
18 
19 #include "stdio.h"	/* for stdout, stderr */
20 #include "string.h"	/* for strcpy */
21 #include "sys/types.h"	/* for time_t */
22 #include "time.h"	/* for struct tm */
23 #include "stdlib.h"	/* for exit, malloc, atoi */
24 #include <err.h>
25 #include "float.h"	/* for FLT_MAX and DBL_MAX */
26 #include "ctype.h"	/* for isalpha et al. */
27 #ifndef isascii
28 #define isascii(x) 1
29 #endif /* !defined isascii */
30 
31 #ifndef ZDUMP_LO_YEAR
32 #define ZDUMP_LO_YEAR	(-500)
33 #endif /* !defined ZDUMP_LO_YEAR */
34 
35 #ifndef ZDUMP_HI_YEAR
36 #define ZDUMP_HI_YEAR	2500
37 #endif /* !defined ZDUMP_HI_YEAR */
38 
39 #ifndef MAX_STRING_LENGTH
40 #define MAX_STRING_LENGTH	1024
41 #endif /* !defined MAX_STRING_LENGTH */
42 
43 #ifndef TRUE
44 #define TRUE		1
45 #endif /* !defined TRUE */
46 
47 #ifndef FALSE
48 #define FALSE		0
49 #endif /* !defined FALSE */
50 
51 #ifndef EXIT_SUCCESS
52 #define EXIT_SUCCESS	0
53 #endif /* !defined EXIT_SUCCESS */
54 
55 #ifndef EXIT_FAILURE
56 #define EXIT_FAILURE	1
57 #endif /* !defined EXIT_FAILURE */
58 
59 #ifndef SECSPERMIN
60 #define SECSPERMIN	60
61 #endif /* !defined SECSPERMIN */
62 
63 #ifndef MINSPERHOUR
64 #define MINSPERHOUR	60
65 #endif /* !defined MINSPERHOUR */
66 
67 #ifndef SECSPERHOUR
68 #define SECSPERHOUR	(SECSPERMIN * MINSPERHOUR)
69 #endif /* !defined SECSPERHOUR */
70 
71 #ifndef HOURSPERDAY
72 #define HOURSPERDAY	24
73 #endif /* !defined HOURSPERDAY */
74 
75 #ifndef EPOCH_YEAR
76 #define EPOCH_YEAR	1970
77 #endif /* !defined EPOCH_YEAR */
78 
79 #ifndef TM_YEAR_BASE
80 #define TM_YEAR_BASE	1900
81 #endif /* !defined TM_YEAR_BASE */
82 
83 #ifndef DAYSPERNYEAR
84 #define DAYSPERNYEAR	365
85 #endif /* !defined DAYSPERNYEAR */
86 
87 #ifndef isleap
88 #define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
89 #endif /* !defined isleap */
90 
91 #ifndef isleap_sum
92 /*
93 ** See tzfile.h for details on isleap_sum.
94 */
95 #define isleap_sum(a, b)	isleap((a) % 400 + (b) % 400)
96 #endif /* !defined isleap_sum */
97 
98 #define SECSPERDAY	((long) SECSPERHOUR * HOURSPERDAY)
99 #define SECSPERNYEAR	(SECSPERDAY * DAYSPERNYEAR)
100 #define SECSPERLYEAR	(SECSPERNYEAR + SECSPERDAY)
101 
102 #ifndef HAVE_GETTEXT
103 #define HAVE_GETTEXT 0
104 #endif
105 #if HAVE_GETTEXT
106 #include "locale.h"	/* for setlocale */
107 #include "libintl.h"
108 #endif /* HAVE_GETTEXT */
109 
110 #ifndef GNUC_or_lint
111 #ifdef lint
112 #define GNUC_or_lint
113 #else /* !defined lint */
114 #ifdef __GNUC__
115 #define GNUC_or_lint
116 #endif /* defined __GNUC__ */
117 #endif /* !defined lint */
118 #endif /* !defined GNUC_or_lint */
119 
120 #ifndef __pure
121 #if 2 < __GNUC__ || (__GNUC__ == 2 && 96 <= __GNUC_MINOR__)
122 # define __pure __attribute__ ((__pure__))
123 #else
124 # define __pure /* empty */
125 #endif
126 #endif
127 
128 #ifndef INITIALIZE
129 #ifdef GNUC_or_lint
130 #define INITIALIZE(x)	((x) = 0)
131 #else /* !defined GNUC_or_lint */
132 #define INITIALIZE(x)
133 #endif /* !defined GNUC_or_lint */
134 #endif /* !defined INITIALIZE */
135 
136 /*
137 ** For the benefit of GNU folk...
138 ** `_(MSGID)' uses the current locale's message library string for MSGID.
139 ** The default is to use gettext if available, and use MSGID otherwise.
140 */
141 
142 #ifndef _
143 #if HAVE_GETTEXT
144 #define _(msgid) gettext(msgid)
145 #else /* !HAVE_GETTEXT */
146 #define _(msgid) msgid
147 #endif /* !HAVE_GETTEXT */
148 #endif /* !defined _ */
149 
150 #ifndef TZ_DOMAIN
151 #define TZ_DOMAIN "tz"
152 #endif /* !defined TZ_DOMAIN */
153 
154 extern char **	environ;
155 extern int	getopt(int argc, char * const argv[],
156 			const char * options);
157 extern char *	optarg;
158 extern int	optind;
159 
160 static time_t	absolute_min_time;
161 static time_t	absolute_max_time;
162 static size_t	longest;
163 static char *	progname;
164 static int	warned;
165 
166 static const char *	abbr(struct tm * tmp);
167 static void	abbrok(const char * abbrp, const char * zone);
168 static long	delta(struct tm * newp, struct tm * oldp) __pure;
169 static void	dumptime(const struct tm * tmp);
170 static time_t	hunt(char * name, time_t lot, time_t	hit);
171 int		main(int, char **);
172 static void	setabsolutes(void);
173 static void	show(char * zone, time_t t, int v);
174 static const char *	tformat(void);
175 static time_t	yeartot(long y) __pure;
176 
177 #ifndef TYPECHECK
178 #define my_localtime	localtime
179 #else /* !defined TYPECHECK */
180 static struct tm *
181 my_localtime(time_t *tp)
182 {
183 	struct tm *tmp;
184 
185 	tmp = localtime(tp);
186 	if (tp != NULL && tmp != NULL) {
187 		struct tm	tm;
188 		time_t	t;
189 
190 		tm = *tmp;
191 		t = mktime(&tm);
192 		if (t - *tp >= 1 || *tp - t >= 1) {
193 			(void) fflush(stdout);
194 			(void) fprintf(stderr, "\n%s: ", progname);
195 			(void) fprintf(stderr, tformat(), *tp);
196 			(void) fprintf(stderr, " ->");
197 			(void) fprintf(stderr, " year=%d", tmp->tm_year);
198 			(void) fprintf(stderr, " mon=%d", tmp->tm_mon);
199 			(void) fprintf(stderr, " mday=%d", tmp->tm_mday);
200 			(void) fprintf(stderr, " hour=%d", tmp->tm_hour);
201 			(void) fprintf(stderr, " min=%d", tmp->tm_min);
202 			(void) fprintf(stderr, " sec=%d", tmp->tm_sec);
203 			(void) fprintf(stderr, " isdst=%d", tmp->tm_isdst);
204 			(void) fprintf(stderr, " -> ");
205 			(void) fprintf(stderr, tformat(), t);
206 			(void) fprintf(stderr, "\n");
207 		}
208 	}
209 	return tmp;
210 }
211 #endif /* !defined TYPECHECK */
212 
213 static void
214 abbrok(const char *const abbrp, const char *const zone)
215 {
216 	const char *cp;
217 	const char *wp;
218 
219 	if (warned)
220 		return;
221 	cp = abbrp;
222 	wp = NULL;
223 	while (isascii((unsigned char) *cp) && isalpha((unsigned char) *cp))
224 		++cp;
225 	if (cp - abbrp == 0)
226 		wp = _("lacks alphabetic at start");
227 	else if (cp - abbrp < 3)
228 		wp = _("has fewer than 3 alphabetics");
229 	else if (cp - abbrp > 6)
230 		wp = _("has more than 6 alphabetics");
231 	if (wp == NULL && (*cp == '+' || *cp == '-')) {
232 		++cp;
233 		if (isascii((unsigned char) *cp) &&
234 			isdigit((unsigned char) *cp))
235 				if (*cp++ == '1' && *cp >= '0' && *cp <= '4')
236 					++cp;
237 		if (*cp != '\0')
238 			wp = _("differs from POSIX standard");
239 	}
240 	if (wp == NULL)
241 		return;
242 	(void) fflush(stdout);
243 	(void) fprintf(stderr,
244 		_("%s: warning: zone \"%s\" abbreviation \"%s\" %s\n"),
245 		progname, zone, abbrp, wp);
246 	warned = TRUE;
247 }
248 
249 __dead static void
250 usage(FILE *const stream, const int status)
251 {
252 	(void) fprintf(stream,
253 _("%s: usage is %s [ --version ] [ --help ] [ -v ] [ -c [loyear,]hiyear ] zonename ...\n\
254 \n\
255 Report bugs to tz@elsie.nci.nih.gov.\n"),
256 		       progname, progname);
257 	exit(status);
258 }
259 
260 int
261 main(int argc, char *argv[])
262 {
263 	int		i;
264 	int		c;
265 	int		vflag;
266 	char *		cutarg;
267 	long		cutloyear = ZDUMP_LO_YEAR;
268 	long		cuthiyear = ZDUMP_HI_YEAR;
269 	time_t		cutlotime;
270 	time_t		cuthitime;
271 	char **		fakeenv;
272 	time_t		now;
273 	time_t		t;
274 	time_t		newt;
275 	struct tm	tm;
276 	struct tm	newtm;
277 	struct tm *	tmp;
278 	struct tm *	newtmp;
279 
280 	INITIALIZE(cutlotime);
281 	INITIALIZE(cuthitime);
282 #if HAVE_GETTEXT
283 	(void) setlocale(LC_ALL, "");
284 #ifdef TZ_DOMAINDIR
285 	(void) bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
286 #endif /* defined TEXTDOMAINDIR */
287 	(void) textdomain(TZ_DOMAIN);
288 #endif /* HAVE_GETTEXT */
289 	progname = argv[0];
290 	for (i = 1; i < argc; ++i)
291 		if (strcmp(argv[i], "--version") == 0) {
292 			(void) printf("%s\n", TZVERSION);
293 			exit(EXIT_SUCCESS);
294 		} else if (strcmp(argv[i], "--help") == 0) {
295 			usage(stdout, EXIT_SUCCESS);
296 		}
297 	vflag = 0;
298 	cutarg = NULL;
299 	while ((c = getopt(argc, argv, "c:v")) == 'c' || c == 'v')
300 		if (c == 'v')
301 			vflag = 1;
302 		else	cutarg = optarg;
303 	if ((c != EOF && c != -1) ||
304 		(optind == argc - 1 && strcmp(argv[optind], "=") == 0)) {
305 			usage(stderr, EXIT_FAILURE);
306 	}
307 	if (vflag) {
308 		if (cutarg != NULL) {
309 			long	lo;
310 			long	hi;
311 			char	dummy;
312 
313 			if (sscanf(cutarg, "%ld%c", &hi, &dummy) == 1) {
314 				cuthiyear = hi;
315 			} else if (sscanf(cutarg, "%ld,%ld%c",
316 				&lo, &hi, &dummy) == 2) {
317 					cutloyear = lo;
318 					cuthiyear = hi;
319 			} else {
320 (void) fprintf(stderr, _("%s: wild -c argument %s\n"),
321 					progname, cutarg);
322 				exit(EXIT_FAILURE);
323 			}
324 		}
325 		setabsolutes();
326 		cutlotime = yeartot(cutloyear);
327 		cuthitime = yeartot(cuthiyear);
328 	}
329 	(void) time(&now);
330 	longest = 0;
331 	for (i = optind; i < argc; ++i)
332 		if (strlen(argv[i]) > longest)
333 			longest = strlen(argv[i]);
334 	{
335 		int	from;
336 		int	to;
337 
338 		for (i = 0; environ[i] != NULL; ++i)
339 			continue;
340 		fakeenv = malloc((i + 2) * sizeof *fakeenv);
341 		if (fakeenv == NULL ||
342 			(fakeenv[0] = malloc(longest + 4)) == NULL) {
343 			err(EXIT_FAILURE, "Can't allocated %zu bytes",
344 			    longest + 4);
345 		}
346 		to = 0;
347 		(void)strcpy(fakeenv[to++], "TZ=");	/* XXX strcpy is safe */
348 		for (from = 0; environ[from] != NULL; ++from)
349 			if (strncmp(environ[from], "TZ=", 3) != 0)
350 				fakeenv[to++] = environ[from];
351 		fakeenv[to] = NULL;
352 		environ = fakeenv;
353 	}
354 	for (i = optind; i < argc; ++i) {
355 		static char	buf[MAX_STRING_LENGTH];
356 
357 		(void) strcpy(&fakeenv[0][3], argv[i]);	/* XXX strcpy is safe */
358 		if (!vflag) {
359 			show(argv[i], now, FALSE);
360 			continue;
361 		}
362 		warned = FALSE;
363 		t = absolute_min_time;
364 		show(argv[i], t, TRUE);
365 		t += SECSPERHOUR * HOURSPERDAY;
366 		show(argv[i], t, TRUE);
367 		if (t < cutlotime)
368 			t = cutlotime;
369 		tmp = my_localtime(&t);
370 		if (tmp != NULL) {
371 			tm = *tmp;
372 			(void) strncpy(buf, abbr(&tm), (sizeof buf) - 1);
373 		}
374 		for ( ; ; ) {
375 			if (t >= cuthitime || t >= cuthitime - SECSPERHOUR * 12)
376 				break;
377 			newt = t + SECSPERHOUR * 12;
378 			newtmp = localtime(&newt);
379 			if (newtmp != NULL)
380 				newtm = *newtmp;
381 			if ((tmp == NULL || newtmp == NULL) ? (tmp != newtmp) :
382 				(delta(&newtm, &tm) != (newt - t) ||
383 				newtm.tm_isdst != tm.tm_isdst ||
384 				strcmp(abbr(&newtm), buf) != 0)) {
385 					newt = hunt(argv[i], t, newt);
386 					newtmp = localtime(&newt);
387 					if (newtmp != NULL) {
388 						newtm = *newtmp;
389 						(void) strncpy(buf,
390 							abbr(&newtm),
391 							(sizeof buf) - 1);
392 					}
393 			}
394 			t = newt;
395 			tm = newtm;
396 			tmp = newtmp;
397 		}
398 		t = absolute_max_time;
399 		t -= SECSPERHOUR * HOURSPERDAY;
400 		show(argv[i], t, TRUE);
401 		t += SECSPERHOUR * HOURSPERDAY;
402 		show(argv[i], t, TRUE);
403 	}
404 	if (fflush(stdout) || ferror(stdout)) {
405 		err(EXIT_FAILURE, _("Error writing standard output"));
406 	}
407 	exit(EXIT_SUCCESS);
408 	/* If exit fails to exit... */
409 	return EXIT_FAILURE;
410 }
411 
412 static time_t
413 ovfl_check(time_t t)
414 {
415 	if (t < 0 && t - 1 >= 0)
416 		return t;
417 	else
418 		return t - 1;
419 }
420 
421 static void
422 setabsolutes(void)
423 {
424 	if (0.5 == (time_t) 0.5) {
425 		/*
426 		** time_t is floating.
427 		*/
428 		if (sizeof (time_t) == sizeof (float)) {
429 			absolute_min_time = (time_t) -FLT_MAX;
430 			absolute_max_time = (time_t) FLT_MAX;
431 		} else if (sizeof (time_t) == sizeof (double)) {
432 			absolute_min_time = (time_t) -DBL_MAX;
433 			absolute_max_time = (time_t) DBL_MAX;
434 		} else {
435 			(void) fprintf(stderr,
436 _("%s: use of -v on system with floating time_t other than float or double\n"),
437 				progname);
438 			exit(EXIT_FAILURE);
439 		}
440 	} else if (0 > (time_t) -1) {
441 		/*
442 		** time_t is signed.  Assume overflow wraps around.
443 		*/
444 		time_t t = 0;
445 		time_t t1 = 1;
446 
447 		while (t < t1) {
448 			t = t1;
449 			t1 = 2 * t1 + 1;
450 		}
451 
452 		absolute_max_time = t;
453 		t = -t;
454 		absolute_min_time = ovfl_check(t);
455 	} else {
456 		/*
457 		** time_t is unsigned.
458 		*/
459 		absolute_min_time = 0;
460 		absolute_max_time = absolute_min_time - 1;
461 	}
462 }
463 
464 static time_t
465 yeartot(const long y)
466 {
467 	long	myy;
468 	long	seconds;
469 	time_t	t;
470 
471 	myy = EPOCH_YEAR;
472 	t = 0;
473 	while (myy != y) {
474 		if (myy < y) {
475 			seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
476 			++myy;
477 			if (t > absolute_max_time - seconds) {
478 				t = absolute_max_time;
479 				break;
480 			}
481 			t += seconds;
482 		} else {
483 			--myy;
484 			seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
485 			if (t < absolute_min_time + seconds) {
486 				t = absolute_min_time;
487 				break;
488 			}
489 			t -= seconds;
490 		}
491 	}
492 	return t;
493 }
494 
495 static time_t
496 hunt(char *name, time_t lot, time_t hit)
497 {
498 	time_t			t;
499 	long			diff;
500 	struct tm		lotm;
501 	struct tm *	lotmp;
502 	struct tm		tm;
503 	struct tm *	tmp;
504 	char			loab[MAX_STRING_LENGTH];
505 
506 	lotmp = my_localtime(&lot);
507 	if (lotmp != NULL) {
508 		lotm = *lotmp;
509 		(void) strncpy(loab, abbr(&lotm), (sizeof loab) - 1);
510 	}
511 	for ( ; ; ) {
512 		diff = (long) (hit - lot);
513 		if (diff < 2)
514 			break;
515 		t = lot;
516 		t += diff / 2;
517 		if (t <= lot)
518 			++t;
519 		else if (t >= hit)
520 			--t;
521 		tmp = my_localtime(&t);
522 		if (tmp != NULL)
523 			tm = *tmp;
524 		if ((lotmp == NULL || tmp == NULL) ? (lotmp == tmp) :
525 			(delta(&tm, &lotm) == (t - lot) &&
526 			tm.tm_isdst == lotm.tm_isdst &&
527 			strcmp(abbr(&tm), loab) == 0)) {
528 				lot = t;
529 				lotm = tm;
530 				lotmp = tmp;
531 		} else	hit = t;
532 	}
533 	show(name, lot, TRUE);
534 	show(name, hit, TRUE);
535 	return hit;
536 }
537 
538 /*
539 ** Thanks to Paul Eggert for logic used in delta.
540 */
541 
542 static long
543 delta(struct tm *newp, struct tm *oldp)
544 {
545 	long	result;
546 	int	tmy;
547 
548 	if (newp->tm_year < oldp->tm_year)
549 		return -delta(oldp, newp);
550 	result = 0;
551 	for (tmy = oldp->tm_year; tmy < newp->tm_year; ++tmy)
552 		result += DAYSPERNYEAR + isleap_sum(tmy, TM_YEAR_BASE);
553 	result += newp->tm_yday - oldp->tm_yday;
554 	result *= HOURSPERDAY;
555 	result += newp->tm_hour - oldp->tm_hour;
556 	result *= MINSPERHOUR;
557 	result += newp->tm_min - oldp->tm_min;
558 	result *= SECSPERMIN;
559 	result += newp->tm_sec - oldp->tm_sec;
560 	return result;
561 }
562 
563 static void
564 show(char *zone, time_t t, int v)
565 {
566 	struct tm *	tmp;
567 
568 	(void) printf("%-*s  ", (int) longest, zone);
569 	if (v) {
570 		tmp = gmtime(&t);
571 		if (tmp == NULL) {
572 			(void) printf(tformat(), t);
573 		} else {
574 			dumptime(tmp);
575 			(void) printf(" UTC");
576 		}
577 		(void) printf(" = ");
578 	}
579 	tmp = my_localtime(&t);
580 	dumptime(tmp);
581 	if (tmp != NULL) {
582 		if (*abbr(tmp) != '\0')
583 			(void) printf(" %s", abbr(tmp));
584 		if (v) {
585 			(void) printf(" isdst=%d", tmp->tm_isdst);
586 #ifdef TM_GMTOFF
587 			(void) printf(" gmtoff=%ld", tmp->TM_GMTOFF);
588 #endif /* defined TM_GMTOFF */
589 		}
590 	}
591 	(void) printf("\n");
592 	if (tmp != NULL && *abbr(tmp) != '\0')
593 		abbrok(abbr(tmp), zone);
594 }
595 
596 static const char *
597 abbr(struct tm *tmp)
598 {
599 	const char *	result;
600 	static const char	nada;
601 
602 	if (tmp->tm_isdst != 0 && tmp->tm_isdst != 1)
603 		return &nada;
604 	result = tzname[tmp->tm_isdst];
605 	return (result == NULL) ? &nada : result;
606 }
607 
608 /*
609 ** The code below can fail on certain theoretical systems;
610 ** it works on all known real-world systems as of 2004-12-30.
611 */
612 
613 static const char *
614 tformat(void)
615 {
616 	if (0.5 == (time_t) 0.5) {	/* floating */
617 		if (sizeof (time_t) > sizeof (double))
618 			return "%Lg";
619 		return "%g";
620 	}
621 	if (0 > (time_t) -1) {		/* signed */
622 		if (sizeof (time_t) > sizeof (long))
623 			return "%lld";
624 		if (sizeof (time_t) > sizeof (int))
625 			return "%ld";
626 		return "%d";
627 	}
628 	if (sizeof (time_t) > sizeof (unsigned long))
629 		return "%llu";
630 	if (sizeof (time_t) > sizeof (unsigned int))
631 		return "%lu";
632 	return "%u";
633 }
634 
635 static void
636 dumptime(const struct tm *timeptr)
637 {
638 	static const char	wday_name[][3] = {
639 		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
640 	};
641 	static const char	mon_name[][3] = {
642 		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
643 		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
644 	};
645 	const char *	wn;
646 	const char *	mn;
647 	int		lead;
648 	int		trail;
649 
650 	if (timeptr == NULL) {
651 		(void) printf("NULL");
652 		return;
653 	}
654 	/*
655 	** The packaged versions of localtime and gmtime never put out-of-range
656 	** values in tm_wday or tm_mon, but since this code might be compiled
657 	** with other (perhaps experimental) versions, paranoia is in order.
658 	*/
659 	if (timeptr->tm_wday < 0 || timeptr->tm_wday >=
660 		(int) (sizeof wday_name / sizeof wday_name[0]))
661 			wn = "???";
662 	else		wn = wday_name[timeptr->tm_wday];
663 	if (timeptr->tm_mon < 0 || timeptr->tm_mon >=
664 		(int) (sizeof mon_name / sizeof mon_name[0]))
665 			mn = "???";
666 	else		mn = mon_name[timeptr->tm_mon];
667 	(void) printf("%.3s %.3s%3d %.2d:%.2d:%.2d ",
668 		wn, mn,
669 		timeptr->tm_mday, timeptr->tm_hour,
670 		timeptr->tm_min, timeptr->tm_sec);
671 #define DIVISOR	10
672 	trail = timeptr->tm_year % DIVISOR + TM_YEAR_BASE % DIVISOR;
673 	lead = timeptr->tm_year / DIVISOR + TM_YEAR_BASE / DIVISOR +
674 		trail / DIVISOR;
675 	trail %= DIVISOR;
676 	if (trail < 0 && lead > 0) {
677 		trail += DIVISOR;
678 		--lead;
679 	} else if (lead < 0 && trail > 0) {
680 		trail -= DIVISOR;
681 		++lead;
682 	}
683 	if (lead == 0)
684 		(void) printf("%d", trail);
685 	else	(void) printf("%d%d", lead, ((trail < 0) ? -trail : trail));
686 }
687