datetime.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * datetime.c
 *	  Support functions for date/time types.
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/adt/datetime.c,v 1.160.2.2 2005/12/01 17:56:43 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <errno.h>
#include <float.h>
#include <limits.h>
#include <math.h>

#include "access/xact.h"
#include "miscadmin.h"
#include "utils/datetime.h"
#include "utils/guc.h"


static int DecodeNumber(int flen, char *field, bool haveTextMonth,
			 int fmask, int *tmask,
			 struct pg_tm * tm, fsec_t *fsec, int *is2digits);
static int DecodeNumberField(int len, char *str,
				  int fmask, int *tmask,
				  struct pg_tm * tm, fsec_t *fsec, int *is2digits);
static int DecodeTime(char *str, int fmask, int *tmask,
		   struct pg_tm * tm, fsec_t *fsec);
static int	DecodeTimezone(char *str, int *tzp);
static int	DecodePosixTimezone(char *str, int *tzp);
static datetkn *datebsearch(char *key, datetkn *base, unsigned int nel);
static int	DecodeDate(char *str, int fmask, int *tmask, struct pg_tm * tm);
static void TrimTrailingZeros(char *str);


const int	day_tab[2][13] =
{
	{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0},
	{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0}
};

char	   *months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec", NULL};

char	   *days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday", NULL};


/*****************************************************************************
 *	 PRIVATE ROUTINES														 *
 *****************************************************************************/

/*
 * Definitions for squeezing values into "value"
 * We set aside a high bit for a sign, and scale the timezone offsets
 * in minutes by a factor of 15 (so can represent quarter-hour increments).
 */
#define ABS_SIGNBIT		((char) 0200)
#define VALMASK			((char) 0177)
#define POS(n)			(n)
#define NEG(n)			((n)|ABS_SIGNBIT)
#define SIGNEDCHAR(c)	((c)&ABS_SIGNBIT? -((c)&VALMASK): (c))
#define FROMVAL(tp)		(-SIGNEDCHAR((tp)->value) * 15) /* uncompress */
#define TOVAL(tp, v)	((tp)->value = ((v) < 0? NEG((-(v))/15): POS(v)/15))

/*
 * datetktbl holds date/time keywords.
 *
 * Note that this table must be strictly alphabetically ordered to allow an
 * O(ln(N)) search algorithm to be used.
 *
 * The text field is NOT guaranteed to be NULL-terminated.
 *
 * To keep this table reasonably small, we divide the lexval for TZ and DTZ
 * entries by 15 (so they are on 15 minute boundaries) and truncate the text
 * field at TOKMAXLEN characters.
 * Formerly, we divided by 10 rather than 15 but there are a few time zones
 * which are 30 or 45 minutes away from an even hour, most are on an hour
 * boundary, and none on other boundaries.
 *
 * Let's include all strings from my current zic time zone database.
 * Not all of them are unique, or even very understandable, so we will
 * leave some commented out for now.
 */
static datetkn datetktbl[] = {
/*	text, token, lexval */
	{EARLY, RESERV, DTK_EARLY}, /* "-infinity" reserved for "early time" */
	{"abstime", IGNORE_DTF, 0}, /* for pre-v6.1 "Invalid Abstime" */
	{"acsst", DTZ, POS(42)},	/* Cent. Australia */
	{"acst", DTZ, NEG(16)},		/* Atlantic/Porto Acre Summer Time */
	{"act", TZ, NEG(20)},		/* Atlantic/Porto Acre Time */
	{DA_D, ADBC, AD},			/* "ad" for years > 0 */
	{"adt", DTZ, NEG(12)},		/* Atlantic Daylight Time */
	{"aesst", DTZ, POS(44)},	/* E. Australia */
	{"aest", TZ, POS(40)},		/* Australia Eastern Std Time */
	{"aft", TZ, POS(18)},		/* Kabul */
	{"ahst", TZ, NEG(40)},		/* Alaska-Hawaii Std Time */
	{"akdt", DTZ, NEG(32)},		/* Alaska Daylight Time */
	{"akst", DTZ, NEG(36)},		/* Alaska Standard Time */
	{"allballs", RESERV, DTK_ZULU},		/* 00:00:00 */
	{"almst", TZ, POS(28)},		/* Almaty Savings Time */
	{"almt", TZ, POS(24)},		/* Almaty Time */
	{"am", AMPM, AM},
	{"amst", DTZ, POS(20)},		/* Armenia Summer Time (Yerevan) */
#if 0
	{"amst", DTZ, NEG(12)},		/* Amazon Summer Time (Porto Velho) */
#endif
	{"amt", TZ, POS(16)},		/* Armenia Time (Yerevan) */
#if 0
	{"amt", TZ, NEG(16)},		/* Amazon Time (Porto Velho) */
#endif
	{"anast", DTZ, POS(52)},	/* Anadyr Summer Time (Russia) */
	{"anat", TZ, POS(48)},		/* Anadyr Time (Russia) */
	{"apr", MONTH, 4},
	{"april", MONTH, 4},
#if 0
	aqtst
	aqtt
	arst
#endif
	{"art", TZ, NEG(12)},		/* Argentina Time */
#if 0
	ashst
	ast							/* Atlantic Standard Time, Arabia Standard
								 * Time, Acre Standard Time */
#endif
	{"ast", TZ, NEG(16)},		/* Atlantic Std Time (Canada) */
	{"at", IGNORE_DTF, 0},		/* "at" (throwaway) */
	{"aug", MONTH, 8},
	{"august", MONTH, 8},
	{"awsst", DTZ, POS(36)},	/* W. Australia */
	{"awst", TZ, POS(32)},		/* W. Australia */
	{"awt", DTZ, NEG(12)},
	{"azost", DTZ, POS(0)},		/* Azores Summer Time */
	{"azot", TZ, NEG(4)},		/* Azores Time */
	{"azst", DTZ, POS(20)},		/* Azerbaijan Summer Time */
	{"azt", TZ, POS(16)},		/* Azerbaijan Time */
	{DB_C, ADBC, BC},			/* "bc" for years <= 0 */
	{"bdst", TZ, POS(8)},		/* British Double Summer Time */
	{"bdt", TZ, POS(24)},		/* Dacca */
	{"bnt", TZ, POS(32)},		/* Brunei Darussalam Time */
	{"bort", TZ, POS(32)},		/* Borneo Time (Indonesia) */
#if 0
	bortst
	bost
#endif
	{"bot", TZ, NEG(16)},		/* Bolivia Time */
	{"bra", TZ, NEG(12)},		/* Brazil Time */
	{"brst", DTZ, NEG(8)},		/* Brasilia Summer Time */
	{"brt", TZ, NEG(12)},		/* Brasilia Time */
	{"bst", DTZ, POS(4)},		/* British Summer Time */
#if 0
	{"bst", TZ, NEG(12)},		/* Brazil Standard Time */
	{"bst", DTZ, NEG(44)},		/* Bering Summer Time */
#endif
	{"bt", TZ, POS(12)},		/* Baghdad Time */
	{"btt", TZ, POS(24)},		/* Bhutan Time */
	{"cadt", DTZ, POS(42)},		/* Central Australian DST */
	{"cast", TZ, POS(38)},		/* Central Australian ST */
	{"cat", TZ, NEG(40)},		/* Central Alaska Time */
	{"cct", TZ, POS(32)},		/* China Coast Time */
#if 0
	{"cct", TZ, POS(26)},		/* Indian Cocos (Island) Time */
#endif
	{"cdt", DTZ, NEG(20)},		/* Central Daylight Time */
	{"cest", DTZ, POS(8)},		/* Central European Dayl.Time */
	{"cet", TZ, POS(4)},		/* Central European Time */
	{"cetdst", DTZ, POS(8)},	/* Central European Dayl.Time */
	{"chadt", DTZ, POS(55)},	/* Chatham Island Daylight Time (13:45) */
	{"chast", TZ, POS(51)},		/* Chatham Island Time (12:45) */
#if 0
	ckhst
#endif
	{"ckt", TZ, POS(48)},		/* Cook Islands Time */
	{"clst", DTZ, NEG(12)},		/* Chile Summer Time */
	{"clt", TZ, NEG(16)},		/* Chile Time */
#if 0
	cost
#endif
	{"cot", TZ, NEG(20)},		/* Columbia Time */
	{"cst", TZ, NEG(24)},		/* Central Standard Time */
	{DCURRENT, RESERV, DTK_CURRENT},	/* "current" is always now */
#if 0
	cvst
#endif
	{"cvt", TZ, POS(28)},		/* Christmas Island Time (Indian Ocean) */
	{"cxt", TZ, POS(28)},		/* Christmas Island Time (Indian Ocean) */
	{"d", UNITS, DTK_DAY},		/* "day of month" for ISO input */
	{"davt", TZ, POS(28)},		/* Davis Time (Antarctica) */
	{"ddut", TZ, POS(40)},		/* Dumont-d'Urville Time (Antarctica) */
	{"dec", MONTH, 12},
	{"december", MONTH, 12},
	{"dnt", TZ, POS(4)},		/* Dansk Normal Tid */
	{"dow", RESERV, DTK_DOW},	/* day of week */
	{"doy", RESERV, DTK_DOY},	/* day of year */
	{"dst", DTZMOD, 6},
#if 0
	{"dusst", DTZ, POS(24)},	/* Dushanbe Summer Time */
#endif
	{"easst", DTZ, NEG(20)},	/* Easter Island Summer Time */
	{"east", TZ, NEG(24)},		/* Easter Island Time */
	{"eat", TZ, POS(12)},		/* East Africa Time */
#if 0
	{"east", DTZ, POS(16)},		/* Indian Antananarivo Savings Time */
	{"eat", TZ, POS(12)},		/* Indian Antananarivo Time */
	{"ect", TZ, NEG(16)},		/* Eastern Caribbean Time */
	{"ect", TZ, NEG(20)},		/* Ecuador Time */
#endif
	{"edt", DTZ, NEG(16)},		/* Eastern Daylight Time */
	{"eest", DTZ, POS(12)},		/* Eastern Europe Summer Time */
	{"eet", TZ, POS(8)},		/* East. Europe, USSR Zone 1 */
	{"eetdst", DTZ, POS(12)},	/* Eastern Europe Daylight Time */
	{"egst", DTZ, POS(0)},		/* East Greenland Summer Time */
	{"egt", TZ, NEG(4)},		/* East Greenland Time */
#if 0
	ehdt
#endif
	{EPOCH, RESERV, DTK_EPOCH}, /* "epoch" reserved for system epoch time */
	{"est", TZ, NEG(20)},		/* Eastern Standard Time */
	{"feb", MONTH, 2},
	{"february", MONTH, 2},
	{"fjst", DTZ, NEG(52)},		/* Fiji Summer Time (13 hour offset!) */
	{"fjt", TZ, NEG(48)},		/* Fiji Time */
	{"fkst", DTZ, NEG(12)},		/* Falkland Islands Summer Time */
	{"fkt", TZ, NEG(8)},		/* Falkland Islands Time */
	{"fnst", DTZ, NEG(4)},		/* Fernando de Noronha Summer Time */
	{"fnt", TZ, NEG(8)},		/* Fernando de Noronha Time */
	{"fri", DOW, 5},
	{"friday", DOW, 5},
	{"fst", TZ, POS(4)},		/* French Summer Time */
	{"fwt", DTZ, POS(8)},		/* French Winter Time  */
	{"galt", TZ, NEG(24)},		/* Galapagos Time */
	{"gamt", TZ, NEG(36)},		/* Gambier Time */
	{"gest", DTZ, POS(20)},		/* Georgia Summer Time */
	{"get", TZ, POS(16)},		/* Georgia Time */
	{"gft", TZ, NEG(12)},		/* French Guiana Time */
#if 0
	ghst
#endif
	{"gilt", TZ, POS(48)},		/* Gilbert Islands Time */
	{"gmt", TZ, POS(0)},		/* Greenwich Mean Time */
	{"gst", TZ, POS(40)},		/* Guam Std Time, USSR Zone 9 */
	{"gyt", TZ, NEG(16)},		/* Guyana Time */
	{"h", UNITS, DTK_HOUR},		/* "hour" */
#if 0
	hadt
	hast
#endif
	{"hdt", DTZ, NEG(36)},		/* Hawaii/Alaska Daylight Time */
#if 0
	hkst
#endif
	{"hkt", TZ, POS(32)},		/* Hong Kong Time */
#if 0
	{"hmt", TZ, POS(12)},		/* Hellas ? ? */
	hovst
	hovt
#endif
	{"hst", TZ, NEG(40)},		/* Hawaii Std Time */
#if 0
	hwt
#endif
	{"ict", TZ, POS(28)},		/* Indochina Time */
	{"idle", TZ, POS(48)},		/* Intl. Date Line, East */
	{"idlw", TZ, NEG(48)},		/* Intl. Date Line, West */
#if 0
	idt							/* Israeli, Iran, Indian Daylight Time */
#endif
	{LATE, RESERV, DTK_LATE},	/* "infinity" reserved for "late time" */
	{INVALID, RESERV, DTK_INVALID},		/* "invalid" reserved for bad time */
	{"iot", TZ, POS(20)},		/* Indian Chagos Time */
	{"irkst", DTZ, POS(36)},	/* Irkutsk Summer Time */
	{"irkt", TZ, POS(32)},		/* Irkutsk Time */
	{"irt", TZ, POS(14)},		/* Iran Time */
#if 0
	isst
#endif
	{"ist", TZ, POS(8)},		/* Israel */
	{"it", TZ, POS(14)},		/* Iran Time */
	{"j", UNITS, DTK_JULIAN},
	{"jan", MONTH, 1},
	{"january", MONTH, 1},
	{"javt", TZ, POS(28)},		/* Java Time (07:00? see JT) */
	{"jayt", TZ, POS(36)},		/* Jayapura Time (Indonesia) */
	{"jd", UNITS, DTK_JULIAN},
	{"jst", TZ, POS(36)},		/* Japan Std Time,USSR Zone 8 */
	{"jt", TZ, POS(30)},		/* Java Time (07:30? see JAVT) */
	{"jul", MONTH, 7},
	{"julian", UNITS, DTK_JULIAN},
	{"july", MONTH, 7},
	{"jun", MONTH, 6},
	{"june", MONTH, 6},
	{"kdt", DTZ, POS(40)},		/* Korea Daylight Time */
	{"kgst", DTZ, POS(24)},		/* Kyrgyzstan Summer Time */
	{"kgt", TZ, POS(20)},		/* Kyrgyzstan Time */
	{"kost", TZ, POS(48)},		/* Kosrae Time */
	{"krast", DTZ, POS(28)},	/* Krasnoyarsk Summer Time */
	{"krat", TZ, POS(32)},		/* Krasnoyarsk Standard Time */
	{"kst", TZ, POS(36)},		/* Korea Standard Time */
	{"lhdt", DTZ, POS(44)},		/* Lord Howe Daylight Time, Australia */
	{"lhst", TZ, POS(42)},		/* Lord Howe Standard Time, Australia */
	{"ligt", TZ, POS(40)},		/* From Melbourne, Australia */
	{"lint", TZ, POS(56)},		/* Line Islands Time (Kiribati; +14 hours!) */
	{"lkt", TZ, POS(24)},		/* Lanka Time */
	{"m", UNITS, DTK_MONTH},	/* "month" for ISO input */
	{"magst", DTZ, POS(48)},	/* Magadan Summer Time */
	{"magt", TZ, POS(44)},		/* Magadan Time */
	{"mar", MONTH, 3},
	{"march", MONTH, 3},
	{"mart", TZ, NEG(38)},		/* Marquesas Time */
	{"mawt", TZ, POS(24)},		/* Mawson, Antarctica */
	{"may", MONTH, 5},
	{"mdt", DTZ, NEG(24)},		/* Mountain Daylight Time */
	{"mest", DTZ, POS(8)},		/* Middle Europe Summer Time */
	{"met", TZ, POS(4)},		/* Middle Europe Time */
	{"metdst", DTZ, POS(8)},	/* Middle Europe Daylight Time */
	{"mewt", TZ, POS(4)},		/* Middle Europe Winter Time */
	{"mez", TZ, POS(4)},		/* Middle Europe Zone */
	{"mht", TZ, POS(48)},		/* Kwajalein */
	{"mm", UNITS, DTK_MINUTE},	/* "minute" for ISO input */
	{"mmt", TZ, POS(26)},		/* Myanmar Time */
	{"mon", DOW, 1},
	{"monday", DOW, 1},
#if 0
	most
#endif
	{"mpt", TZ, POS(40)},		/* North Mariana Islands Time */
	{"msd", DTZ, POS(16)},		/* Moscow Summer Time */
	{"msk", TZ, POS(12)},		/* Moscow Time */
	{"mst", TZ, NEG(28)},		/* Mountain Standard Time */
	{"mt", TZ, POS(34)},		/* Moluccas Time */
	{"mut", TZ, POS(16)},		/* Mauritius Island Time */
	{"mvt", TZ, POS(20)},		/* Maldives Island Time */
	{"myt", TZ, POS(32)},		/* Malaysia Time */
#if 0
	ncst
#endif
	{"nct", TZ, POS(44)},		/* New Caledonia Time */
	{"ndt", DTZ, NEG(10)},		/* Nfld. Daylight Time */
	{"nft", TZ, NEG(14)},		/* Newfoundland Standard Time */
	{"nor", TZ, POS(4)},		/* Norway Standard Time */
	{"nov", MONTH, 11},
	{"november", MONTH, 11},
	{"novst", DTZ, POS(28)},	/* Novosibirsk Summer Time */
	{"novt", TZ, POS(24)},		/* Novosibirsk Standard Time */
	{NOW, RESERV, DTK_NOW},		/* current transaction time */
	{"npt", TZ, POS(23)},		/* Nepal Standard Time (GMT-5:45) */
	{"nst", TZ, NEG(14)},		/* Nfld. Standard Time */
	{"nt", TZ, NEG(44)},		/* Nome Time */
	{"nut", TZ, NEG(44)},		/* Niue Time */
	{"nzdt", DTZ, POS(52)},		/* New Zealand Daylight Time */
	{"nzst", TZ, POS(48)},		/* New Zealand Standard Time */
	{"nzt", TZ, POS(48)},		/* New Zealand Time */
	{"oct", MONTH, 10},
	{"october", MONTH, 10},
	{"omsst", DTZ, POS(28)},	/* Omsk Summer Time */
	{"omst", TZ, POS(24)},		/* Omsk Time */
	{"on", IGNORE_DTF, 0},		/* "on" (throwaway) */
	{"pdt", DTZ, NEG(28)},		/* Pacific Daylight Time */
#if 0
	pest
#endif
	{"pet", TZ, NEG(20)},		/* Peru Time */
	{"petst", DTZ, POS(52)},	/* Petropavlovsk-Kamchatski Summer Time */
	{"pett", TZ, POS(48)},		/* Petropavlovsk-Kamchatski Time */
	{"pgt", TZ, POS(40)},		/* Papua New Guinea Time */
	{"phot", TZ, POS(52)},		/* Phoenix Islands (Kiribati) Time */
#if 0
	phst
#endif
	{"pht", TZ, POS(32)},		/* Phillipine Time */
	{"pkt", TZ, POS(20)},		/* Pakistan Time */
	{"pm", AMPM, PM},
	{"pmdt", DTZ, NEG(8)},		/* Pierre & Miquelon Daylight Time */
#if 0
	pmst
#endif
	{"pont", TZ, POS(44)},		/* Ponape Time (Micronesia) */
	{"pst", TZ, NEG(32)},		/* Pacific Standard Time */
	{"pwt", TZ, POS(36)},		/* Palau Time */
	{"pyst", DTZ, NEG(12)},		/* Paraguay Summer Time */
	{"pyt", TZ, NEG(16)},		/* Paraguay Time */
	{"ret", DTZ, POS(16)},		/* Reunion Island Time */
	{"s", UNITS, DTK_SECOND},	/* "seconds" for ISO input */
	{"sadt", DTZ, POS(42)},		/* S. Australian Dayl. Time */
#if 0
	samst
	samt
#endif
	{"sast", TZ, POS(38)},		/* South Australian Std Time */
	{"sat", DOW, 6},
	{"saturday", DOW, 6},
#if 0
	sbt
#endif
	{"sct", DTZ, POS(16)},		/* Mahe Island Time */
	{"sep", MONTH, 9},
	{"sept", MONTH, 9},
	{"september", MONTH, 9},
	{"set", TZ, NEG(4)},		/* Seychelles Time ?? */
#if 0
	sgt
#endif
	{"sst", DTZ, POS(8)},		/* Swedish Summer Time */
	{"sun", DOW, 0},
	{"sunday", DOW, 0},
	{"swt", TZ, POS(4)},		/* Swedish Winter Time */
#if 0
	syot
#endif
	{"t", ISOTIME, DTK_TIME},	/* Filler for ISO time fields */
	{"tft", TZ, POS(20)},		/* Kerguelen Time */
	{"that", TZ, NEG(40)},		/* Tahiti Time */
	{"thu", DOW, 4},
	{"thur", DOW, 4},
	{"thurs", DOW, 4},
	{"thursday", DOW, 4},
	{"tjt", TZ, POS(20)},		/* Tajikistan Time */
	{"tkt", TZ, NEG(40)},		/* Tokelau Time */
	{"tmt", TZ, POS(20)},		/* Turkmenistan Time */
	{TODAY, RESERV, DTK_TODAY}, /* midnight */
	{TOMORROW, RESERV, DTK_TOMORROW},	/* tomorrow midnight */
#if 0
	tost
#endif
	{"tot", TZ, POS(52)},		/* Tonga Time */
#if 0
	tpt
#endif
	{"truk", TZ, POS(40)},		/* Truk Time */
	{"tue", DOW, 2},
	{"tues", DOW, 2},
	{"tuesday", DOW, 2},
	{"tvt", TZ, POS(48)},		/* Tuvalu Time */
#if 0
	uct
#endif
	{"ulast", DTZ, POS(36)},	/* Ulan Bator Summer Time */
	{"ulat", TZ, POS(32)},		/* Ulan Bator Time */
	{"undefined", RESERV, DTK_INVALID}, /* pre-v6.1 invalid time */
	{"ut", TZ, POS(0)},
	{"utc", TZ, POS(0)},
	{"uyst", DTZ, NEG(8)},		/* Uruguay Summer Time */
	{"uyt", TZ, NEG(12)},		/* Uruguay Time */
	{"uzst", DTZ, POS(24)},		/* Uzbekistan Summer Time */
	{"uzt", TZ, POS(20)},		/* Uzbekistan Time */
	{"vet", TZ, NEG(16)},		/* Venezuela Time */
	{"vlast", DTZ, POS(44)},	/* Vladivostok Summer Time */
	{"vlat", TZ, POS(40)},		/* Vladivostok Time */
#if 0
	vust
#endif
	{"vut", TZ, POS(44)},		/* Vanuata Time */
	{"wadt", DTZ, POS(32)},		/* West Australian DST */
	{"wakt", TZ, POS(48)},		/* Wake Time */
#if 0
	warst
#endif
	{"wast", TZ, POS(28)},		/* West Australian Std Time */
	{"wat", TZ, NEG(4)},		/* West Africa Time */
	{"wdt", DTZ, POS(36)},		/* West Australian DST */
	{"wed", DOW, 3},
	{"wednesday", DOW, 3},
	{"weds", DOW, 3},
	{"west", DTZ, POS(4)},		/* Western Europe Summer Time */
	{"wet", TZ, POS(0)},		/* Western Europe */
	{"wetdst", DTZ, POS(4)},	/* Western Europe Daylight Savings Time */
	{"wft", TZ, POS(48)},		/* Wallis and Futuna Time */
	{"wgst", DTZ, NEG(8)},		/* West Greenland Summer Time */
	{"wgt", TZ, NEG(12)},		/* West Greenland Time */
	{"wst", TZ, POS(32)},		/* West Australian Standard Time */
	{"y", UNITS, DTK_YEAR},		/* "year" for ISO input */
	{"yakst", DTZ, POS(40)},	/* Yakutsk Summer Time */
	{"yakt", TZ, POS(36)},		/* Yakutsk Time */
	{"yapt", TZ, POS(40)},		/* Yap Time (Micronesia) */
	{"ydt", DTZ, NEG(32)},		/* Yukon Daylight Time */
	{"yekst", DTZ, POS(24)},	/* Yekaterinburg Summer Time */
	{"yekt", TZ, POS(20)},		/* Yekaterinburg Time */
	{YESTERDAY, RESERV, DTK_YESTERDAY}, /* yesterday midnight */
	{"yst", TZ, NEG(36)},		/* Yukon Standard Time */
	{"z", TZ, POS(0)},			/* time zone tag per ISO-8601 */
	{"zp4", TZ, NEG(16)},		/* UTC +4  hours. */
	{"zp5", TZ, NEG(20)},		/* UTC +5  hours. */
	{"zp6", TZ, NEG(24)},		/* UTC +6  hours. */
	{ZULU, TZ, POS(0)},			/* UTC */
};

static unsigned int szdatetktbl = sizeof datetktbl / sizeof datetktbl[0];