NAME
parsedate - convert time and date string to number
SYNOPSIS
#include <sys/types.h>
typedef struct _TIMEINFO {
time_t time;
long usec;
long tzone;
} TIMEINFO;
time_t
parsedate(text, now)
char *text;
TIMEINFO *now;
DESCRIPTION
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.
BUGS
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.
HISTORY
Originally written by Steven M. Bellovin <smb@research.att.com> while
at the University of North Carolina at Chapel Hill and distributed
under the name getdate.
A major overhaul was done by Rich $alz <rsalz@bbn.com> and Jim Berets
<jberets@bbn.com> in August, 1990.
It was further revised (primarily to remove obsolete constructs and
timezone names) a year later by Rich (now <rsalz@osf.org>) for
InterNetNews, and the name was changed. This is revision 1.10, dated
1993/01/29.
SEE ALSO
date(1), ctime(3), libinn(3), time(2).