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 lib
inn(3) is used to obtain the current time and timezone.
The character string consists of zero or more specifica
tions 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, mon
thname 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
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 dif
ferences.
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 con
structs and timezone names) a year later by Rich (now
<rsalz@osf.org>) for InterNetNews, and the name was
changed. This is revision 1.1.1.1, dated 1997/08/04.
SEE ALSO
date(1), ctime(3), libinn(3), time(2).
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