.TH GETABSDATE 3 "8 February 1995"
.SH NAME
getabsdate, prsabsdate, getindate, prsindate \- date and time parsers
.SH SYNOPSIS
.ft B
.nf
#include <sys/types.h>
#include <sys/timeb.h>
.sp 0.3
time_t getabsdate(str, now)
char *str;
struct timeb *now;
.sp 0.3
time_t getindate(str, now)
char *str;
struct timeb *now;
.sp 0.3
#include <time.h>
.sp 0.3
int prsabsdate(str, now, tm, tzp)
char *str;
struct timeb *now;
struct tm *tm;
int *tzp;
.sp 0.3
int prsindate(str, tm, tzp)
char *str;
struct tm *tm;
int *tzp;
.fi
.ft
.SH DESCRIPTION
.I Getabsdate
and
.I getindate
parse dates
(in
.IR str )
and convert them to
.I time_t s
(seconds since the epoch).
.I Prsabsdate
and
.I prsindate
parse dates and produce
broken-out time structures and time zones instead.
All are faster and smaller than
.IR get_date (3).
.I Getindate
and
.I prsindate
are faster than
.I getabsdate
and
.IR prsabsdate ,
but
.I getindate
and
.I prsindate
only parse Internet dates
(as specified in Internet RFCs 822 and 1123).
.PP
.I Getabsdate
and
.I prsabsdate
parse fairly arbitrary absolute dates:
each date must contain a day-of-month,
English month name,
and two- or four-digit year,
and may optionally contain
a colon-separated time
(with optional seconds) (defaults to 00:00:00),
weekday name,
and signed numeric or alphabetic time zone (defaults to local time).
The day-of-month must precede the year,
but no other ordering is assumed.
Four-digit years are encouraged.
Delimiters are space,
tab,
newline,
slash,
and comma;
dashes are only delimiters if the date cannot otherwise be parsed.
All-numeric dates are ambiguous and are rejected.
Unknown words are assumed to be bogus timezones and are ignored.
American military time zones are not supported.
Alphabetic time zones other than GMT are deprecated.
.PP
.I Getindate
and
.I prsindate
parse RFC 822 dates,
as amended by RFC 1123
(GMT is strongly encouraged).
These routines are intended to be used to parse dates
suspected to be machine-generated or otherwise likely to be in
the right format.
Due to their extreme speed,
they may be used as a pre-pass before calling
.I getabsdate
or
.I prsabsdate
in any case.
.\" .SH FILES
.SH SEE ALSO
.IR ctime (3),
.IR mktime (3)
.br
Internet RFCs 822 and 1123
.SH DIAGNOSTICS
All return a negative value on error.
.SH HISTORY
Written at the University of Toronto
by Geoff Collyer and Mark Moraes
(who regret ever getting involved with date parsing).
Bits of code borrowed with permission from
.IR get_date (3),
Rayan Zachariassen and Rich Wales.
Corrections to the time zone table from Paul Eggert.
.SH BUGS
.I Getabsdate
and
.I prsabsdate
modify their
.I str
arguments.
.PP
Using local time as the default time zone is okay,
but it should be local time
.IR then ,
at the specified date and time,
whereas in fact the time zone that is used is local time
.IR now .
(For example, if daylight savings time is in effect when
.I getabsdate
is called,
.I getabsdate
will assume it is always in effect.)
This is hard to fix without better information on
time changes.
.PP
The treatment of dashes in
.I getabsdate
and
.I prsabsdate
is a hack to permit parsing of dates in DEC format
(31-Jan-91),
which is itself a botch,
so we're even.
.PP
Alphabetic time zones are wildly ambiguous;
don't use them.
.PP
The Gregorian calendar is a kludge only an innumerate could love.
When will someone impose a metric calendar and free us from the
vanity and incompetence of the Roman emperors,
notably the random lengths of months?
.PP
Daylight savings time is a patchwork mess only a politician could love.
.PP
Weekday names are too long and redundant.
Did the Norse have weak memories?
.PP
Leap years are a pain;
the earth should be stabilised.