%{
/* Parse a string into an internal time stamp.
   Copyright 1999, 2000 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Originally written by Steven M. Bellovin <smb@research.att.com> while
   at the University of North Carolina at Chapel Hill.  Later tweaked by
   a couple of people on Usenet.  Completely overhauled by Rich $alz
   <rsalz@bbn.com> and Jim Berets <jberets@bbn.com> in August, 1990.

   Modified by Paul Eggert <eggert@twinsun.com> in August 1999 to do
   the right thing about local DST.  Unlike previous versions, this
   version is reentrant.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
# ifdef HAVE_ALLOCA_H
#  include <alloca.h>
# endif
#endif

/* Since the code of getdate.y is not included in the Emacs executable
   itself, there is no need to #define static in this file.  Even if
   the code were included in the Emacs executable, it probably
   wouldn't do any harm to #undef it here; this will only cause
   problems if we try to write to a static variable, which I don't
   think this code needs to do.  */
#ifdef emacs
# undef static
#endif

#include <ctype.h>

#if HAVE_STDLIB_H
# include <stdlib.h> /* for `free'; used by Bison 1.27 */
#endif

#if STDC_HEADERS || (! defined isascii && ! HAVE_ISASCII)
# define IN_CTYPE_DOMAIN(c) 1
#else
# define IN_CTYPE_DOMAIN(c) isascii (c)
#endif

#define ISSPACE(c) (IN_CTYPE_DOMAIN (c) && isspace (c))
#define ISALPHA(c) (IN_CTYPE_DOMAIN (c) && isalpha (c))
#define ISLOWER(c) (IN_CTYPE_DOMAIN (c) && islower (c))
#define ISDIGIT_LOCALE(c) (IN_CTYPE_DOMAIN (c) && isdigit (c))

/* ISDIGIT differs from ISDIGIT_LOCALE, as follows:
   - Its arg may be any int or unsigned int; it need not be an unsigned char.
   - It's guaranteed to evaluate its argument exactly once.
   - It's typically faster.
   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
   only '0' through '9' are digits.  Prefer ISDIGIT to ISDIGIT_LOCALE unless
   it's important to use the locale's definition of `digit' even when the
   host does not conform to Posix.  */
#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)

#if STDC_HEADERS || HAVE_STRING_H
# include <string.h>
#endif

#if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8) || __STRICT_ANSI__
# define __attribute__(x)
#endif

#ifndef ATTRIBUTE_UNUSED
# define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
#endif

#define EPOCH_YEAR 1970
#define TM_YEAR_BASE 1900

#define HOUR(x) ((x) * 60)
 
/* An integer value, and the number of digits in its textual
   representation.  */
typedef struct
{
  int value;
  int digits;
} textint;

/* An entry in the lexical lookup table.  */
typedef struct
{
  char const *name;
  int type;
  int value;
} table;

/* Meridian: am, pm, or 24-hour style.  */
enum { MERam, MERpm, MER24 };

/* Information passed to and from the parser.  */
typedef struct
{
  /* The input string remaining to be parsed. */
  const char *input;

  /* N, if this is the Nth Tuesday.  */
  int day_ordinal;

  /* Day of week; Sunday is 0.  */
  int day_number;

  /* tm_isdst flag for the local zone.  */
  int local_isdst;

  /* Time zone, in minutes east of UTC.  */
  int time_zone;

  /* Style used for time.  */
  int meridian;

  /* Gregorian year, month, day, hour, minutes, and seconds.  */
  textint year;
  int month;
  int day;
  int hour;
  int minutes;
  int seconds;

  /* Relative year, month, day, hour, minutes, and seconds.  */
  int rel_year;
  int rel_month;
  int rel_day;
  int rel_hour;
  int rel_minutes;
  int rel_seconds;

  /* Counts of nonterminals of various flavors parsed so far.  */
  int dates_seen;
  int days_seen;
  int local_zones_seen;
  int rels_seen;
  int times_seen;
  int zones_seen;

  /* Table of local time zone abbrevations, terminated by a null entry.  */
  table local_time_zone_table[3];
} parser_control;

#define PC (* (parser_control *) parm)
#define YYLEX_PARAM parm
#define YYPARSE_PARAM parm

static int yyerror ();
static int yylex ();

%}

/* We want a reentrant parser.  */
%pure_parser

/* This grammar has 13 shift/reduce conflicts. */
%expect 13
 
%union
{
  int intval;
  textint textintval;
}

%token tAGO tDST

%token <intval> tDAY tDAY_UNIT tDAYZONE tHOUR_UNIT tLOCAL_ZONE tMERIDIAN
%token <intval> tMINUTE_UNIT tMONTH tMONTH_UNIT tSEC_UNIT tYEAR_UNIT tZONE

%token <textintval> tSNUMBER tUNUMBER

%type <intval> o_merid

%%

spec:
    /* empty */
  | spec item
  ;

item:
    time
      { PC.times_seen++; }
  | local_zone
      { PC.local_zones_seen++; }
  | zone
      { PC.zones_seen++; }
  | date
      { PC.dates_seen++; }
  | day
      { PC.days_seen++; }
  | rel
      { PC.rels_seen++; }
  | number
  ;

time:
    tUNUMBER tMERIDIAN
      {
	PC.hour = $1.value;
	PC.minutes = 0;
	PC.seconds = 0;
	PC.meridian = $2;
      }
  | tUNUMBER ':' tUNUMBER o_merid
      {
	PC.hour = $1.value;
	PC.minutes = $3.value;
	PC.seconds = 0;
	PC.meridian = $4;
      }
  | tUNUMBER ':' tUNUMBER tSNUMBER
      {
	PC.hour = $1.value;
	PC.minutes = $3.value;
	PC.meridian = MER24;
	PC.zones_seen++;
	PC.time_zone = $4.value % 100 + ($4.value / 100) * 60;
      }
  | tUNUMBER ':' tUNUMBER ':' tUNUMBER o_merid
      {
	PC.hour = $1.value;
	PC.minutes = $3.value;
	PC.seconds = $5.value;
	PC.meridian = $6;
      }
  | tUNUMBER ':' tUNUMBER ':' tUNUMBER tSNUMBER
      {
	PC.hour = $1.value;
	PC.minutes = $3.value;
	PC.seconds = $5.value;
	PC.meridian = MER24;
	PC.zones_seen++;
	PC.time_zone = $6.value % 100 + ($6.value / 100) * 60;
      }
  ;

local_zone:
    tLOCAL_ZONE
      { PC.local_isdst = $1; }
  | tLOCAL_ZONE tDST
      { PC.local_isdst = $1 < 0 ? 1 : $1 + 1; }
  ;

zone:
    tZONE
      { PC.time_zone = $1; }
  | tDAYZONE
      { PC.time_zone = $1 + 60; }
  | tZONE tDST
      { PC.time_zone = $1 + 60; }
  ;

day:
    tDAY
      {
	PC.day_ordinal = 1;
	PC.day_number = $1;
      }
  | tDAY ','
      {
	PC.day_ordinal = 1;
	PC.day_number = $1;
      }
  | tUNUMBER tDAY
      {
	PC.day_ordinal = $1.value;
	PC.day_number = $2;
      }
  ;

date:
    tUNUMBER '/' tUNUMBER
      {
	PC.month = $1.value;
	PC.day = $3.value;
      }
  | tUNUMBER '/' tUNUMBER '/' tUNUMBER
      {
	/* Interpret as YYYY/MM/DD if the first value has 4 or more digits,
	   otherwise as MM/DD/YY.
	   The goal in recognizing YYYY/MM/DD is solely to support legacy
	   machine-generated dates like those in an RCS log listing.  If
	   you want portability, use the ISO 8601 format.  */
	if (4 <= $1.digits)
	  {
	    PC.year = $1;
	    PC.month = $3.value;
	    PC.day = $5.value;
	  }
	else
	  {
	    PC.month = $1.value;
	    PC.day = $3.value;
	    PC.year = $5;
	  }
      }
  | tUNUMBER tSNUMBER tSNUMBER
      {
	/* ISO 8601 format.  YYYY-MM-DD.  */
	PC.year = $1;
	PC.month = -$2.value;
	PC.day = -$3.value;
      }
  | tUNUMBER tMONTH tSNUMBER
      {
	/* e.g. 17-JUN-1992.  */
	PC.day = $1.value;
	PC.month = $2;
	PC.year.value = -$3.value;
	PC.year.digits = $3.digits;
      }
  | tMONTH tUNUMBER
      {
	PC.month = $1;
	PC.day = $2.value;
      }
  | tMONTH tUNUMBER ',' tUNUMBER
      {
	PC.month = $1;
	PC.day = $2.value;
	PC.year = $4;
      }
  | tUNUMBER tMONTH
      {
	PC.day = $1.value;
	PC.month = $2;
      }
  | tUNUMBER tMONTH tUNUMBER
      {
	PC.day = $1.value;
	PC.month = $2;
	PC.year = $3;
      }
  ;

rel:
    relunit tAGO
      {
	PC.rel_seconds = -PC.rel_seconds;
	PC.rel_minutes = -PC.rel_minutes;
	PC.rel_hour = -PC.rel_hour;
	PC.rel_day = -PC.rel_day;
	PC.rel_month = -PC.rel_month;
	PC.rel_year = -PC.rel_year;
      }
  | relunit
  ;

relunit:
    tUNUMBER tYEAR_UNIT
      { PC.rel_year += $1.value * $2; }
  | tSNUMBER tYEAR_UNIT
      { PC.rel_year += $1.value * $2; }
  | tYEAR_UNIT
      { PC.rel_year += $1; }
  | tUNUMBER tMONTH_UNIT
      { PC.rel_month += $1.value * $2; }
  | tSNUMBER tMONTH_UNIT
      { PC.rel_month += $1.value * $2; }
  | tMONTH_UNIT
      { PC.rel_month += $1; }
  | tUNUMBER tDAY_UNIT
      { PC.rel_day += $1.value * $2; }
  | tSNUMBER tDAY_UNIT
      { PC.rel_day += $1.value * $2; }
  | tDAY_UNIT
      { PC.rel_day += $1 }
  | tUNUMBER tHOUR_UNIT
      { PC.rel_hour += $1.value * $2; }
  | tSNUMBER tHOUR_UNIT
      { PC.rel_hour += $1.value * $2; }
  | tHOUR_UNIT
      { PC.rel_hour += $1 }
  | tUNUMBER tMINUTE_UNIT
      { PC.rel_minutes += $1.value * $2; }
  | tSNUMBER tMINUTE_UNIT
      { PC.rel_minutes += $1.value * $2; }
  | tMINUTE_UNIT
      { PC.rel_minutes += $1 }
  | tUNUMBER tSEC_UNIT
      { PC.rel_seconds += $1.value * $2; }
  | tSNUMBER tSEC_UNIT
      { PC.rel_seconds += $1.value * $2; }
  | tSEC_UNIT
      { PC.rel_seconds += $1; }
  ;

number:
    tUNUMBER
      {
	if (PC.dates_seen
	    && ! PC.rels_seen && (PC.times_seen || 2 < $1.digits))
	  PC.year = $1;
	else
	  {
	    if (4 < $1.digits)
	      {
		PC.dates_seen++;
		PC.day = $1.value % 100;
		PC.month = ($1.value / 100) % 100;
		PC.year.value = $1.value / 10000;
		PC.year.digits = $1.digits - 4;
	      }
	    else
	      {
		PC.times_seen++;
		if ($1.digits <= 2)
		  {
		    PC.hour = $1.value;
		    PC.minutes = 0;
		  }
		else
		  {
		    PC.hour = $1.value / 100;
		    PC.minutes = $1.value % 100;
		  }
		PC.seconds = 0;
		PC.meridian = MER24;
	      }
	  }
      }
  ;

o_merid:
    /* empty */
      { $$ = MER24; }
  | tMERIDIAN
      { $$ = $1; }
  ;

%%

/* Include this file down here because bison inserts code above which
   may define-away `const'.  We want the prototype for get_date to have
   the same signature as the function definition.  */
#include "getdate.h"

#ifndef gmtime
struct tm *gmtime ();
#endif
#ifndef localtime
struct tm *localtime ();
#endif
#ifndef mktime
time_t mktime ();
#endif

static table const meridian_table[] =
{
  { "AM",   tMERIDIAN, MERam },
  { "A.M.", tMERIDIAN, MERam },
  { "PM",   tMERIDIAN, MERpm },
  { "P.M.", tMERIDIAN, MERpm },
  { 0, 0, 0 }
};

static table const dst_table[] =
{
  { "DST", tDST, 0 }
};

static table const month_and_day_table[] =
{
  { "JANUARY",	tMONTH,	 1 },
  { "FEBRUARY",	tMONTH,	 2 },
  { "MARCH",	tMONTH,	 3 },
  { "APRIL",	tMONTH,	 4 },
  { "MAY",	tMONTH,	 5 },
  { "JUNE",	tMONTH,	 6 },
  { "JULY",	tMONTH,	 7 },
  { "AUGUST",	tMONTH,	 8 },
  { "SEPTEMBER",tMONTH,	 9 },
  { "SEPT",	tMONTH,	 9 },
  { "OCTOBER",	tMONTH,	10 },
  { "NOVEMBER",	tMONTH,	11 },
  { "DECEMBER",	tMONTH,	12 },
  { "SUNDAY",	tDAY,	 0 },
  { "MONDAY",	tDAY,	 1 },
  { "TUESDAY",	tDAY,	 2 },
  { "TUES",	tDAY,	 2 },
  { "WEDNESDAY",tDAY,	 3 },
  { "WEDNES",	tDAY,	 3 },
  { "THURSDAY",	tDAY,	 4 },
  { "THUR",	tDAY,	 4 },
  { "THURS",	tDAY,	 4 },
  { "FRIDAY",	tDAY,	 5 },
  { "SATURDAY",	tDAY,	 6 },
  { 0, 0, 0 }
};

static table const time_units_table[] =
{
  { "YEAR",	tYEAR_UNIT,	 1 },
  { "MONTH",	tMONTH_UNIT,	 1 },
  { "FORTNIGHT",tDAY_UNIT,	14 },
  { "WEEK",	tDAY_UNIT,	 7 },
  { "DAY",	tDAY_UNIT,	 1 },
  { "HOUR",	tHOUR_UNIT,	 1 },
  { "MINUTE",	tMINUTE_UNIT,	 1 },
  { "MIN",	tMINUTE_UNIT,	 1 },
  { "SECOND",	tSEC_UNIT,	 1 },
  { "SEC",	tSEC_UNIT,	 1 },
  { 0, 0, 0 }
};

/* Assorted relative-time words. */
static table const relative_time_table[] =
{
  { "TOMORROW",	tMINUTE_UNIT,	24 * 60 },
  { "YESTERDAY",tMINUTE_UNIT,	- (24 * 60) },
  { "TODAY",	tMINUTE_UNIT,	 0 },
  { "NOW",	tMINUTE_UNIT,	 0 },
  { "LAST",	tUNUMBER,	-1 },
  { "THIS",	tUNUMBER,	 0 },
  { "NEXT",	tUNUMBER,	 1 },
  { "FIRST",	tUNUMBER,	 1 },
/*{ "SECOND",	tUNUMBER,	 2 }, */
  { "THIRD",	tUNUMBER,	 3 },
  { "FOURTH",	tUNUMBER,	 4 },
  { "FIFTH",	tUNUMBER,	 5 },
  { "SIXTH",	tUNUMBER,	 6 },
  { "SEVENTH",	tUNUMBER,	 7 },
  { "EIGHTH",	tUNUMBER,	 8 },
  { "NINTH",	tUNUMBER,	 9 },
  { "TENTH",	tUNUMBER,	10 },
  { "ELEVENTH",	tUNUMBER,	11 },
  { "TWELFTH",	tUNUMBER,	12 },
  { "AGO",	tAGO,		 1 },
  { 0, 0, 0 }
};

/* The time zone table.  This table is necessarily incomplete, as time
   zone abbreviations are ambiguous; e.g. Australians interpret "EST"
   as Eastern time in Australia, not as US Eastern Standard Time.
   You cannot rely on getdate to handle arbitrary time zone
   abbreviations; use numeric abbreviations like `-0500' instead.  */
static table const time_zone_table[] =
{
  { "GMT",	tZONE,     HOUR ( 0) },	/* Greenwich Mean */
  { "UT",	tZONE,     HOUR ( 0) },	/* Universal (Coordinated) */
  { "UTC",	tZONE,     HOUR ( 0) },
  { "WET",	tZONE,     HOUR ( 0) },	/* Western European */
  { "WEST",	tDAYZONE,  HOUR ( 0) },	/* Western European Summer */
  { "BST",	tDAYZONE,  HOUR ( 0) },	/* British Summer */
  { "ART",	tZONE,	  -HOUR ( 3) },	/* Argentina */
  { "BRT",	tZONE,	  -HOUR ( 3) },	/* Brazil */
  { "BRST",	tDAYZONE, -HOUR ( 3) },	/* Brazil Summer */
  { "NST",	tZONE,	 -(HOUR ( 3) + 30) },	/* Newfoundland Standard */
  { "NDT",	tDAYZONE,-(HOUR ( 3) + 30) },	/* Newfoundland Daylight */
  { "AST",	tZONE,    -HOUR ( 4) },	/* Atlantic Standard */
  { "ADT",	tDAYZONE, -HOUR ( 4) },	/* Atlantic Daylight */
  { "CLT",	tZONE,    -HOUR ( 4) },	/* Chile */
  { "CLST",	tDAYZONE, -HOUR ( 4) },	/* Chile Summer */
  { "EST",	tZONE,    -HOUR ( 5) },	/* Eastern Standard */
  { "EDT",	tDAYZONE, -HOUR ( 5) },	/* Eastern Daylight */
  { "CST",	tZONE,    -HOUR ( 6) },	/* Central Standard */
  { "CDT",	tDAYZONE, -HOUR ( 6) },	/* Central Daylight */
  { "MST",	tZONE,    -HOUR ( 7) },	/* Mountain Standard */
  { "MDT",	tDAYZONE, -HOUR ( 7) },	/* Mountain Daylight */
  { "PST",	tZONE,    -HOUR ( 8) },	/* Pacific Standard */
  { "PDT",	tDAYZONE, -HOUR ( 8) },	/* Pacific Daylight */
  { "AKST",	tZONE,    -HOUR ( 9) },	/* Alaska Standard */
  { "AKDT",	tDAYZONE, -HOUR ( 9) },	/* Alaska Daylight */
  { "HST",	tZONE,    -HOUR (10) },	/* Hawaii Standard */
  { "HAST",	tZONE,	  -HOUR (10) },	/* Hawaii-Aleutian Standard */
  { "HADT",	tDAYZONE, -HOUR (10) },	/* Hawaii-Aleutian Daylight */
  { "SST",	tZONE,    -HOUR (12) },	/* Samoa Standard */
  { "WAT",	tZONE,     HOUR ( 1) },	/* West Africa */
  { "CET",	tZONE,     HOUR ( 1) },	/* Central European */
  { "CEST",	tDAYZONE,  HOUR ( 1) },	/* Central European Summer */
  { "MET",	tZONE,     HOUR ( 1) },	/* Middle European */
  { "MEZ",	tZONE,     HOUR ( 1) },	/* Middle European */
  { "MEST",	tDAYZONE,  HOUR ( 1) },	/* Middle European Summer */
  { "MESZ",	tDAYZONE,  HOUR ( 1) },	/* Middle European Summer */
  { "EET",	tZONE,     HOUR ( 2) },	/* Eastern European */
  { "EEST",	tDAYZONE,  HOUR ( 2) },	/* Eastern European Summer */
  { "CAT",	tZONE,	   HOUR ( 2) },	/* Central Africa */
  { "SAST",	tZONE,	   HOUR ( 2) },	/* South Africa Standard */
  { "EAT",	tZONE,	   HOUR ( 3) },	/* East Africa */
  { "MSK",	tZONE,	   HOUR ( 3) },	/* Moscow */
  { "MSD",	tDAYZONE,  HOUR ( 3) },	/* Moscow Daylight */
  { "IST",	tZONE,	  (HOUR ( 5) + 30) },	/* India Standard */
  { "SGT",	tZONE,     HOUR ( 8) },	/* Singapore */
  { "KST",	tZONE,     HOUR ( 9) },	/* Korea Standard */
  { "JST",	tZONE,     HOUR ( 9) },	/* Japan Standard */
  { "GST",	tZONE,     HOUR (10) },	/* Guam Standard */
  { "NZST",	tZONE,     HOUR (12) },	/* New Zealand Standard */
  { "NZDT",	tDAYZONE,  HOUR (12) },	/* New Zealand Daylight */
  { 0, 0, 0  }
};

/* Military time zone table. */
static table const military_table[] =
{
  { "A", tZONE,	-HOUR ( 1) },
  { "B", tZONE,	-HOUR ( 2) },
  { "C", tZONE,	-HOUR ( 3) },
  { "D", tZONE,	-HOUR ( 4) },
  { "E", tZONE,	-HOUR ( 5) },
  { "F", tZONE,	-HOUR ( 6) },
  { "G", tZONE,	-HOUR ( 7) },
  { "H", tZONE,	-HOUR ( 8) },
  { "I", tZONE,	-HOUR ( 9) },
  { "K", tZONE,	-HOUR (10) },
  { "L", tZONE,	-HOUR (11) },
  { "M", tZONE,	-HOUR (12) },
  { "N", tZONE,	 HOUR ( 1) },
  { "O", tZONE,	 HOUR ( 2) },
  { "P", tZONE,	 HOUR ( 3) },
  { "Q", tZONE,	 HOUR ( 4) },
  { "R", tZONE,	 HOUR ( 5) },
  { "S", tZONE,	 HOUR ( 6) },
  { "T", tZONE,	 HOUR ( 7) },
  { "U", tZONE,	 HOUR ( 8) },
  { "V", tZONE,	 HOUR ( 9) },
  { "W", tZONE,	 HOUR (10) },
  { "X", tZONE,	 HOUR (11) },
  { "Y", tZONE,	 HOUR (12) },
  { "Z", tZONE,	 HOUR ( 0) },
  { 0, 0, 0 }
};



static int
to_hour (int hours, int meridian)
{
  switch (meridian)
    {
    case MER24:
      return 0 <= hours && hours < 24 ? hours : -1;
    case MERam:
      return 0 < hours && hours < 12 ? hours : hours == 12 ? 0 : -1;
    case MERpm:
      return 0 < hours && hours < 12 ? hours + 12 : hours == 12 ? 12 : -1;
    default:
      abort ();
    }
  /* NOTREACHED */
}

static int
to_year (textint textyear)
{
  int year = textyear.value;

  if (year < 0)
    year = -year;

  /* XPG4 suggests that years 00-68 map to 2000-2068, and
     years 69-99 map to 1969-1999.  */
  if (textyear.digits == 2)
    year += year < 69 ? 2000 : 1900;

  return year;
}

static table const *
lookup_zone (parser_control const *pc, char const *name)
{
  table const *tp;

  /* Try local zone abbreviations first; they're more likely to be right.  */
  for (tp = pc->local_time_zone_table; tp->name; tp++)
    if (strcmp (name, tp->name) == 0)
      return tp;

  for (tp = time_zone_table; tp->name; tp++)
    if (strcmp (name, tp->name) == 0)
      return tp;

  return 0;
}

#if ! HAVE_TM_GMTOFF
/* Yield the difference between *A and *B,
   measured in seconds, ignoring leap seconds.
   The body of this function is taken directly from the GNU C Library;
   see src/strftime.c.  */
static int
tm_diff (struct tm const *a, struct tm const *b)
{
  /* Compute intervening leap days correctly even if year is negative.
     Take care to avoid int overflow in leap day calculations,
     but it's OK to assume that A and B are close to each other.  */
  int a4 = (a->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (a->tm_year & 3);
  int b4 = (b->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (b->tm_year & 3);
  int a100 = a4 / 25 - (a4 % 25 < 0);
  int b100 = b4 / 25 - (b4 % 25 < 0);
  int a400 = a100 >> 2;
  int b400 = b100 >> 2;
  int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
  int years = a->tm_year - b->tm_year;
  int days = (365 * years + intervening_leap_days
	      + (a->tm_yday - b->tm_yday));
  return (60 * (60 * (24 * days + (a->tm_hour - b->tm_hour))
		+ (a->tm_min - b->tm_min))
	  + (a->tm_sec - b->tm_sec));
}
#endif /* ! HAVE_TM_GMTOFF */

static table const *
lookup_word (parser_control const *pc, char *word)
{
  char *p;
  char *q;
  size_t wordlen;
  table const *tp;
  int i;
  int abbrev;

  /* Make it uppercase.  */
  for (p = word; *p; p++)
    if (ISLOWER ((unsigned char) *p))
      *p = toupper ((unsigned char) *p);

  for (tp = meridian_table; tp->name; tp++)
    if (strcmp (word, tp->name) == 0)
      return tp;

  /* See if we have an abbreviation for a month. */
  wordlen = strlen (word);
  abbrev = wordlen == 3 || (wordlen == 4 && word[3] == '.');

  for (tp = month_and_day_table; tp->name; tp++)
    if ((abbrev ? strncmp (word, tp->name, 3) : strcmp (word, tp->name)) == 0)
      return tp;

  if ((tp = lookup_zone (pc, word)))
    return tp;

  if (strcmp (word, dst_table[0].name) == 0)
    return dst_table;

  for (tp = time_units_table; tp->name; tp++)
    if (strcmp (word, tp->name) == 0)
      return tp;

  /* Strip off any plural and try the units table again. */
  if (word[wordlen - 1] == 'S')
    {
      word[wordlen - 1] = '\0';
      for (tp = time_units_table; tp->name; tp++)
	if (strcmp (word, tp->name) == 0)
	  return tp;
      word[wordlen - 1] = 'S';	/* For "this" in relative_time_table.  */
    }

  for (tp = relative_time_table; tp->name; tp++)
    if (strcmp (word, tp->name) == 0)
      return tp;

  /* Military time zones. */
  if (wordlen == 1)
    for (tp = military_table; tp->name; tp++)
      if (word[0] == tp->name[0])
	return tp;

  /* Drop out any periods and try the time zone table again. */
  for (i = 0, p = q = word; (*p = *q); q++)
    if (*q == '.')
      i = 1;
    else
      p++;
  if (i && (tp = lookup_zone (pc, word)))
    return tp;

  return 0;
}

static int
yylex (YYSTYPE *lvalp, parser_control *pc)
{
  unsigned char c;
  int count;

  for (;;)
    {
      while (c = *pc->input, ISSPACE (c))
	pc->input++;

      if (ISDIGIT (c) || c == '-' || c == '+')
	{
	  char const *p;
	  int sign;
	  int value;
	  if (c == '-' || c == '+')
	    {
	      sign = c == '-' ? -1 : 1;
	      c = *++pc->input;
	      if (! ISDIGIT (c))
		/* skip the '-' sign */
		continue;
	    }
	  else
	    sign = 0;
	  p = pc->input;
	  value = 0;
	  do
	    {
	      value = 10 * value + c - '0';
	      c = *++p;
	    }
	  while (ISDIGIT (c));
	  lvalp->textintval.value = sign < 0 ? -value : value;
	  lvalp->textintval.digits = p - pc->input;
	  pc->input = p;
	  return sign ? tSNUMBER : tUNUMBER;
	}

      if (ISALPHA (c))
	{
	  char buff[20];
	  char *p = buff;
	  table const *tp;

	  do
	    {
	      if (p < buff + sizeof buff - 1)
		*p++ = c;
	      c = *++pc->input;
	    }
	  while (ISALPHA (c) || c == '.');

	  *p = '\0';
	  tp = lookup_word (pc, buff);
	  if (! tp)
	    return '?';
	  lvalp->intval = tp->value;
	  return tp->type;
	}

      if (c != '(')
	return *pc->input++;
      count = 0;
      do
	{
	  c = *pc->input++;
	  if (c == '\0')
	    return c;
	  if (c == '(')
	    count++;
	  else if (c == ')')
	    count--;
	}
      while (count > 0);
    }
}

/* Do nothing if the parser reports an error.  */
static int
yyerror (char *s ATTRIBUTE_UNUSED)
{
  return 0;
}

/* Parse a date/time string P.  Return the corresponding time_t value,
   or (time_t) -1 if there is an error.  P can be an incomplete or
   relative time specification; if so, use *NOW as the basis for the
   returned time.  */
time_t
get_date (const char *p, const time_t *now)
{
  time_t Start = now ? *now : time (0);
  struct tm *tmp = localtime (&Start);
  struct tm tm;
  struct tm tm0;
  parser_control pc;

  if (! tmp)
    return -1;

  pc.input = p;
  pc.year.value = tmp->tm_year + TM_YEAR_BASE;
  pc.year.digits = 4;
  pc.month = tmp->tm_mon + 1;
  pc.day = tmp->tm_mday;
  pc.hour = tmp->tm_hour;
  pc.minutes = tmp->tm_min;
  pc.seconds = tmp->tm_sec;
  tm.tm_isdst = tmp->tm_isdst;

  pc.meridian = MER24;
  pc.rel_seconds = 0;
  pc.rel_minutes = 0;
  pc.rel_hour = 0;
  pc.rel_day = 0;
  pc.rel_month = 0;
  pc.rel_year = 0;
  pc.dates_seen = 0;
  pc.days_seen = 0;
  pc.rels_seen = 0;
  pc.times_seen = 0;
  pc.local_zones_seen = 0;
  pc.zones_seen = 0;

#if HAVE_TM_ZONE
  pc.local_time_zone_table[0].name = tmp->tm_zone;
  pc.local_time_zone_table[0].type = tLOCAL_ZONE;
  pc.local_time_zone_table[0].value = tmp->tm_isdst;
  pc.local_time_zone_table[1].name = 0;

  /* Probe the names used in the next three calendar quarters, looking
     for a tm_isdst different from the one we already have.  */
  {
    int quarter;
    for (quarter = 1; quarter <= 3; quarter++)
      {
	time_t probe = Start + quarter * (90 * 24 * 60 * 60);
	struct tm *probe_tm = localtime (&probe);
	if (probe_tm && probe_tm->tm_zone
	    && probe_tm->tm_isdst != pc.local_time_zone_table[0].value)
	  {
	      {
		pc.local_time_zone_table[1].name = probe_tm->tm_zone;
		pc.local_time_zone_table[1].type = tLOCAL_ZONE;
		pc.local_time_zone_table[1].value = probe_tm->tm_isdst;
		pc.local_time_zone_table[2].name = 0;
	      }
	    break;
	  }
      }
  }
#else
#if HAVE_TZNAME
  {
# ifndef tzname
    extern char *tzname[];
# endif
    int i;
    for (i = 0; i < 2; i++)
      {
	pc.local_time_zone_table[i].name = tzname[i];
	pc.local_time_zone_table[i].type = tLOCAL_ZONE;
	pc.local_time_zone_table[i].value = i;
      }
    pc.local_time_zone_table[i].name = 0;
  }
#else
  pc.local_time_zone_table[0].name = 0;
#endif
#endif

  if (pc.local_time_zone_table[0].name && pc.local_time_zone_table[1].name
      && ! strcmp (pc.local_time_zone_table[0].name,
		   pc.local_time_zone_table[1].name))
    {
      /* This locale uses the same abbrevation for standard and
	 daylight times.  So if we see that abbreviation, we don't
	 know whether it's daylight time.  */
      pc.local_time_zone_table[0].value = -1;
      pc.local_time_zone_table[1].name = 0;
    }

  if (yyparse (&pc) != 0
      || 1 < pc.times_seen || 1 < pc.dates_seen || 1 < pc.days_seen
      || 1 < (pc.local_zones_seen + pc.zones_seen)
      || (pc.local_zones_seen && 1 < pc.local_isdst))
    return -1;

  tm.tm_year = to_year (pc.year) - TM_YEAR_BASE + pc.rel_year;
  tm.tm_mon = pc.month - 1 + pc.rel_month;
  tm.tm_mday = pc.day + pc.rel_day;
  if (pc.times_seen || (pc.rels_seen && ! pc.dates_seen && ! pc.days_seen))
    {
      tm.tm_hour = to_hour (pc.hour, pc.meridian);
      if (tm.tm_hour < 0)
	return -1;
      tm.tm_min = pc.minutes;
      tm.tm_sec = pc.seconds;
    }
  else
    {
      tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
    }
  tm.tm_hour += pc.rel_hour;
  tm.tm_min += pc.rel_minutes;
  tm.tm_sec += pc.rel_seconds;

  /* Let mktime deduce tm_isdst if we have an absolute time stamp,
     or if the relative time stamp mentions days, months, or years.  */
  if (pc.dates_seen | pc.days_seen | pc.times_seen | pc.rel_day | pc.rel_month | pc.rel_year)
    tm.tm_isdst = -1;

  /* But if the input explicitly specifies local time with or without
     DST, give mktime that information.  */
  if (pc.local_zones_seen)
    tm.tm_isdst = pc.local_isdst;

  tm0 = tm;

  Start = mktime (&tm);

  if (Start == (time_t) -1)
    {

      /* Guard against falsely reporting errors near the time_t boundaries
         when parsing times in other time zones.  For example, if the min
         time_t value is 1970-01-01 00:00:00 UTC and we are 8 hours ahead
         of UTC, then the min localtime value is 1970-01-01 08:00:00; if
         we apply mktime to 1970-01-01 00:00:00 we will get an error, so
         we apply mktime to 1970-01-02 08:00:00 instead and adjust the time
         zone by 24 hours to compensate.  This algorithm assumes that
         there is no DST transition within a day of the time_t boundaries.  */
      if (pc.zones_seen)
	{
	  tm = tm0;
	  if (tm.tm_year <= EPOCH_YEAR - TM_YEAR_BASE)
	    {
	      tm.tm_mday++;
	      pc.time_zone += 24 * 60;
	    }
	  else
	    {
	      tm.tm_mday--;
	      pc.time_zone -= 24 * 60;
	    }
	  Start = mktime (&tm);
	}

      if (Start == (time_t) -1)
	return Start;
    }

  if (pc.days_seen && ! pc.dates_seen)
    {
      tm.tm_mday += ((pc.day_number - tm.tm_wday + 7) % 7
		     + 7 * (pc.day_ordinal - (0 < pc.day_ordinal)));
      Start = mktime (&tm);
      if (Start == (time_t) -1)
	return Start;
    }

  if (pc.zones_seen)
    {
      int delta = pc.time_zone * 60;
#ifdef HAVE_TM_GMTOFF
      delta -= tm.tm_gmtoff;
#else
      struct tm *gmt = gmtime (&Start);
      if (! gmt)
	return -1;
      delta -= tm_diff (&tm, gmt);
#endif
      if ((Start < Start - delta) != (delta < 0))
	return -1;	/* time_t overflow */
      Start -= delta;
    }

  return Start;
}

#if TEST

#include <stdio.h>

int
main (int ac, char **av)
{
  char buff[BUFSIZ];
  time_t d;

  printf ("Enter date, or blank line to exit.\n\t> ");
  fflush (stdout);

  buff[BUFSIZ - 1] = 0;
  while (fgets (buff, BUFSIZ - 1, stdin) && buff[0])
    {
      d = get_date (buff, 0);
      if (d == (time_t) -1)
	printf ("Bad format - couldn't convert.\n");
      else
	printf ("%s", ctime (&d));
      printf ("\t> ");
      fflush (stdout);
    }
  return 0;
}
#endif /* defined TEST */