parsedate - convert time and date string to number

     #include <sys/types.h>

     typedef struct _TIMEINFO {
         time_t           time;
         long             usec;
         long             tzone;
     } TIMEINFO;

     parsedate(text, now)
         char             *text;
         TIMEINFO         *now;

     Parsedate converts many common time specifications  into  the  number  of
     seconds since the epoch -- i.e., a time_t; see time(2).

     Parsedate returns the time, or -1 on error.  Text is a  character  string
     containing  the  time and date.  Now is a pointer to the time that should
     be used for calculating relative dates.  If now is NULL, then GetTimeInfo
     in libinn(3) is used to obtain the current time and timezone.

     The character string consists of  zero  or  more  specifications  of  the
     following form:

     time A time of day, which is of the form hh[:mm[:ss]]  [meridian]  [zone]
          or  hhmm  [meridian]  [zone].   If  no  meridian is specified, hh is
          interpreted on a 24-hour clock.

     date A specific month and day with optional year.  The acceptable formats
          are  mm/dd[/yy],  yyyy/mm/dd, monthname dd[, yy], dd monthname [yy],
          and day, dd monthname yy.  The default year is the current year.  If
          the  year  is less then 100, then 1900 is added to it; if it is less
          then 21, then 2000 is added to it.

     relative time
          A specification relative to the current time.  The format is  number
          unit;  acceptable units are year, month, week, day, hour, minute (or
          min), and second (or sec).  The unit can be specified as a  singular
          or plural, as in 3 weeks.

     The actual date is calculated according to the following  steps.   First,
     any  absolute  date  and/or  time is processed and converted.  Using that
     time as the base, day-of-week specifications are added.   Next,  relative
     specifications  are used.  If a date or day is specified, and no absolute
     or relative time is given, midnight is used.  Finally,  a  correction  is
     applied  so  that  the correct hour of the day is produced after allowing
     for daylight savings time differences.

     Parsedate ignores case when parsing all words; unknown words are taken to
     be  unknown timezones, which are treated as GMT.  The names of the months
     and days of the week can be abbreviated to  their  first  three  letters,
     with  optional  trailing  period.  Periods are ignored in any timezone or
     meridian values.
     Parsedate does not accept all desirable  and  unambiguous  constructions.
     Semantically incorrect dates such as ``February 31'' are accepted.

     Daylight savings time is always taken as a one-hour change which is wrong
     for  some  places.  The daylight savings time correction can get confused
     if parsing a time within an hour of when the  reckoning  changes,  or  if
     given a partial date.

     Originally written by Steven M. Bellovin <> while  at
     the University of North Carolina at Chapel Hill and distributed under the
     name getdate.

     A major overhaul was done by Rich $alz  <>  and  Jim  Berets
     <> in August, 1990.

     It was further revised  (primarily  to  remove  obsolete  constructs  and
     timezone   names)   a  year  later  by  Rich  (now  <>)  for
     InterNetNews, and the name was changed.  This  is  revision  1.10,  dated

     date(1), ctime(3), libinn(3) , time(2).

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