case 'x':	/* appropriate date representation */			strftime(tbuf, sizeof tbuf, "%A %B %d %Y", timeptr);			break;		case 'X':	/* appropriate time representation */			goto the_time;			break;		case 'y':	/* year without a century, 00 - 99 */		year:			i = timeptr->tm_year % 100;			sprintf(tbuf, "%02d", i);			break;		case 'Y':	/* year with century */		fullyear:			sprintf(tbuf, "%ld", 1900L + timeptr->tm_year);			break;		/*		 * From: Chip Rosenthal <chip@chinacat.unicom.com>		 * Date: Sun, 19 Mar 1995 00:33:29 -0600 (CST)		 * 		 * Warning: the %z [code] is implemented by inspecting the		 * timezone name conditional compile settings, and		 * inferring a method to get timezone offsets. I've tried		 * this code on a couple of machines, but I don't doubt		 * there is some system out there that won't like it.		 * Maybe the easiest thing to do would be to bracket this		 * with an #ifdef that can turn it off. The %z feature		 * would be an admittedly obscure one that most folks can		 * live without, but it would be a great help to those of		 * us that muck around with various message processors.		 */ 		case 'z':	/* time zone offset east of GMT e.g. -0600 */ 			if (timeptr->tm_isdst < 0) 				break;#ifdef HAVE_TM_NAME			/*			 * Systems with tm_name probably have tm_tzadj as			 * secs west of GMT.  Convert to mins east of GMT.			 */			off = -timeptr->tm_tzadj / 60;#else /* !HAVE_TM_NAME */#ifdef HAVE_TM_ZONE			/*			 * Systems with tm_zone probably have tm_gmtoff as			 * secs east of GMT.  Convert to mins east of GMT.			 */			off = timeptr->tm_gmtoff / 60;#else /* !HAVE_TM_ZONE */#if HAVE_TZNAME			/*			 * Systems with tzname[] probably have timezone as			 * secs west of GMT.  Convert to mins east of GMT.			 */#  ifdef HPUX			off = -timezone / 60;#  else			/* ADR: 4 August 2001, fixed this per gazelle@interaccess.com */			off = -(daylight ? altzone : timezone) / 60;#  endif /* !HPUX */#else /* !HAVE_TZNAME */			gettimeofday(& tv, & zone);			off = -zone.tz_minuteswest;#endif /* !HAVE_TZNAME */#endif /* !HAVE_TM_ZONE */#endif /* !HAVE_TM_NAME */			if (off < 0) {				tbuf[0] = '-';				off = -off;			} else {				tbuf[0] = '+';			}			sprintf(tbuf+1, "%02ld%02ld", off/60, off%60);			break;		case 'Z':	/* time zone name or abbrevation */#ifdef HAVE_TZNAME			i = (daylight && timeptr->tm_isdst > 0); /* 0 or 1 */			strcpy(tbuf, tzname[i]);#else#ifdef HAVE_TM_ZONE			strcpy(tbuf, timeptr->tm_zone);#else#ifdef HAVE_TM_NAME			strcpy(tbuf, timeptr->tm_name);#else			gettimeofday(& tv, & zone);			strcpy(tbuf, timezone(zone.tz_minuteswest,						timeptr->tm_isdst > 0));#endif /* HAVE_TM_NAME */#endif /* HAVE_TM_ZONE */#endif /* HAVE_TZNAME */			break;#ifdef SUNOS_EXT		case 'k':	/* hour, 24-hour clock, blank pad */			sprintf(tbuf, "%2d", range(0, timeptr->tm_hour, 23));			break;		case 'l':	/* hour, 12-hour clock, 1 - 12, blank pad */			i = range(0, timeptr->tm_hour, 23);			if (i == 0)				i = 12;			else if (i > 12)				i -= 12;			sprintf(tbuf, "%2d", i);			break;#endif#ifdef HPUX_EXT		case 'N':	/* Emperor/Era name */			/* this is essentially the same as the century */			goto century;	/* %C */		case 'o':	/* Emperor/Era year */			goto year;	/* %y */#endif /* HPUX_EXT */#ifdef VMS_EXT		case 'v':	/* date as dd-bbb-YYYY */			sprintf(tbuf, "%2d-%3.3s-%4ld",				range(1, timeptr->tm_mday, 31),				months_a[range(0, timeptr->tm_mon, 11)],				timeptr->tm_year + 1900L);			for (i = 3; i < 6; i++)				if (islower(tbuf[i]))					tbuf[i] = toupper(tbuf[i]);			break;#endif		default:			tbuf[0] = '%';			tbuf[1] = *format;			tbuf[2] = '\0';			break;		}		i = strlen(tbuf);		if (i) {			if (s + i < endp - 1) {				strcpy(s, tbuf);				s += i;			} else				return 0;		}	}out:	if (s < endp && *format == '\0') {		*s = '\0';		return (s - start);	} else		return 0;}/* isleap --- is a year a leap year? */static intisleap(long year){	return ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);}/* iso8601wknum --- compute week number according to ISO 8601 */static intiso8601wknum(const struct tm *timeptr){	/*	 * From 1003.2:	 *	If the week (Monday to Sunday) containing January 1	 *	has four or more days in the new year, then it is week 1;	 *	otherwise it is the highest numbered week of the previous	 *	year (52 or 53), and the next week is week 1.	 *	 * ADR: This means if Jan 1 was Monday through Thursday,	 *	it was week 1, otherwise week 52 or 53.	 *	 * XPG4 erroneously included POSIX.2 rationale text in the	 * main body of the standard. Thus it requires week 53.	 */	int weeknum, jan1day, diff;	/* get week number, Monday as first day of the week */	weeknum = weeknumber(timeptr, 1);	/*	 * With thanks and tip of the hatlo to tml@tik.vtt.fi	 *	 * What day of the week does January 1 fall on?	 * We know that	 *	(timeptr->tm_yday - jan1.tm_yday) MOD 7 ==	 *		(timeptr->tm_wday - jan1.tm_wday) MOD 7	 * and that	 * 	jan1.tm_yday == 0	 * and that	 * 	timeptr->tm_wday MOD 7 == timeptr->tm_wday	 * from which it follows that. . . 	 */	jan1day = timeptr->tm_wday - (timeptr->tm_yday % 7);	if (jan1day < 0)		jan1day += 7;	/*	 * If Jan 1 was a Monday through Thursday, it was in	 * week 1.  Otherwise it was last year's highest week, which is	 * this year's week 0.	 *	 * What does that mean?	 * If Jan 1 was Monday, the week number is exactly right, it can	 *	never be 0.	 * If it was Tuesday through Thursday, the weeknumber is one	 *	less than it should be, so we add one.	 * Otherwise, Friday, Saturday or Sunday, the week number is	 * OK, but if it is 0, it needs to be 52 or 53.	 */	switch (jan1day) {	case 1:		/* Monday */		break;	case 2:		/* Tuesday */	case 3:		/* Wednesday */	case 4:		/* Thursday */		weeknum++;		break;	case 5:		/* Friday */	case 6:		/* Saturday */	case 0:		/* Sunday */		if (weeknum == 0) {#ifdef USE_BROKEN_XPG4			/* XPG4 (as of March 1994) says 53 unconditionally */			weeknum = 53;#else			/* get week number of last week of last year */			struct tm dec31ly;	/* 12/31 last year */			dec31ly = *timeptr;			dec31ly.tm_year--;			dec31ly.tm_mon = 11;			dec31ly.tm_mday = 31;			dec31ly.tm_wday = (jan1day == 0) ? 6 : jan1day - 1;			dec31ly.tm_yday = 364 + isleap(dec31ly.tm_year + 1900L);			weeknum = iso8601wknum(& dec31ly);#endif		}		break;	}	if (timeptr->tm_mon == 11) {		/*		 * The last week of the year		 * can be in week 1 of next year.		 * Sigh.		 *		 * This can only happen if		 *	M   T  W		 *	29  30 31		 *	30  31		 *	31		 */		int wday, mday;		wday = timeptr->tm_wday;		mday = timeptr->tm_mday;		if (   (wday == 1 && (mday >= 29 && mday <= 31))		    || (wday == 2 && (mday == 30 || mday == 31))		    || (wday == 3 &&  mday == 31))			weeknum = 1;	}	return weeknum;}/* weeknumber --- figure how many weeks into the year *//* With thanks and tip of the hatlo to ado@elsie.nci.nih.gov */static intweeknumber(const struct tm *timeptr, int firstweekday){	int wday = timeptr->tm_wday;	int ret;	if (firstweekday == 1) {		if (wday == 0)	/* sunday */			wday = 6;		else			wday--;	}	ret = ((timeptr->tm_yday + 7 - wday) / 7);	if (ret < 0)		ret = 0;	return ret;}#if 0/* ADR --- I'm loathe to mess with ado's code ... */Date:         Wed, 24 Apr 91 20:54:08 MDTFrom: Michal Jaegermann <audfax!emory!vm.ucs.UAlberta.CA!NTOMCZAK>To: arnold@audiofax.comHi Arnold,in a process of fixing of strftime() in libraries on Atari ST I grabbedsome pieces of code from your own strftime.  When doing that it cameto mind that your weeknumber() function compiles a little bit nicerin the following form:/* * firstweekday is 0 if starting in Sunday, non-zero if in Monday */{    return (timeptr->tm_yday - timeptr->tm_wday +	    (firstweekday ? (timeptr->tm_wday ? 8 : 1) : 7)) / 7;}How nicer it depends on a compiler, of course, but always a tiny bit.   Cheers,   Michal   ntomczak@vm.ucs.ualberta.ca#endif#ifdef	TEST_STRFTIME/* * NAME: *	tst * * SYNOPSIS: *	tst * * DESCRIPTION: *	"tst" is a test driver for the function "strftime". * * OPTIONS: *	None. * * AUTHOR: *	Karl Vogel *	Control Data Systems, Inc. *	vogelke@c-17igp.wpafb.af.mil * * BUGS: *	None noticed yet. * * COMPILE: *	cc -o tst -DTEST_STRFTIME strftime.c *//* ADR: I reformatted this to my liking, and deleted some unneeded code. */#ifndef NULL#include	<stdio.h>#endif#include	<sys/time.h>#include	<string.h>#define		MAXTIME		132/* * Array of time formats. */static char *array[] ={	"(%%A)      full weekday name, var length (Sunday..Saturday)  %A",	"(%%B)       full month name, var length (January..December)  %B",	"(%%C)                                               Century  %C",	"(%%D)                                       date (%%m/%%d/%%y)  %D",	"(%%E)                           Locale extensions (ignored)  %E",	"(%%F)       full month name, var length (January..December)  %F",	"(%%H)                          hour (24-hour clock, 00..23)  %H",	"(%%I)                          hour (12-hour clock, 01..12)  %I",	"(%%M)                                       minute (00..59)  %M",	"(%%N)                                      Emporer/Era Name  %N",	"(%%O)                           Locale extensions (ignored)  %O",	"(%%R)                                 time, 24-hour (%%H:%%M)  %R",	"(%%S)                                       second (00..60)  %S",	"(%%T)                              time, 24-hour (%%H:%%M:%%S)  %T",	"(%%U)    week of year, Sunday as first day of week (00..53)  %U",	"(%%V)                    week of year according to ISO 8601  %V",	"(%%W)    week of year, Monday as first day of week (00..53)  %W",	"(%%X)     appropriate locale time representation (%H:%M:%S)  %X",	"(%%Y)                           year with century (1970...)  %Y",	"(%%Z) timezone (EDT), or blank if timezone not determinable  %Z",	"(%%a)          locale's abbreviated weekday name (Sun..Sat)  %a",	"(%%b)            locale's abbreviated month name (Jan..Dec)  %b",	"(%%c)           full date (Sat Nov  4 12:02:33 1989)%n%t%t%t  %c",	"(%%d)                             day of the month (01..31)  %d",	"(%%e)               day of the month, blank-padded ( 1..31)  %e",	"(%%h)                                should be same as (%%b)  %h",	"(%%j)                            day of the year (001..366)  %j",	"(%%k)               hour, 24-hour clock, blank pad ( 0..23)  %k",	"(%%l)               hour, 12-hour clock, blank pad ( 0..12)  %l",	"(%%m)                                        month (01..12)  %m",	"(%%o)                                      Emporer/Era Year  %o",	"(%%p)              locale's AM or PM based on 12-hour clock  %p",	"(%%r)                   time, 12-hour (same as %%I:%%M:%%S %%p)  %r",	"(%%u) ISO 8601: Weekday as decimal number [1 (Monday) - 7]   %u",	"(%%v)                                VMS date (dd-bbb-YYYY)  %v",	"(%%w)                       day of week (0..6, Sunday == 0)  %w",	"(%%x)                appropriate locale date representation  %x",	"(%%y)                      last two digits of year (00..99)  %y",	"(%%z)      timezone offset east of GMT as HHMM (e.g. -0500)  %z",	(char *) NULL};/* main routine. */intmain(argc, argv)int argc;char **argv;{	long time();	char *next;	char string[MAXTIME];	int k;	int length;	struct tm *tm;	long clock;	/* Call the function. */	clock = time((long *) 0);	tm = localtime(&clock);	for (k = 0; next = array[k]; k++) {		length = strftime(string, MAXTIME, next, tm);		printf("%s\n", string);	}	exit(0);}#endif	/* TEST_STRFTIME */