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3.8. Printing a Date

3.8.1. Problem

You need to print a date and time
shown in Epoch seconds format in human-readable
form.

3.8.2. Solution

Call
localtime or gmtime in scalar
context, which takes an Epoch seconds value and returns a string of
the form Tue July
22 05:15:20
2003:

$STRING = localtime($EPOCH_SECONDS);

Alternatively,
the strftime function in the standard POSIX module
supports a more customizable output format and takes individual
DMYHMS values:

use POSIX qw(strftime);
$STRING = strftime($FORMAT, $SECONDS, $MINUTES, $HOUR,
$DAY_OF_MONTH, $MONTH, $YEAR, $WEEKDAY,
$YEARDAY, $DST);

The CPAN module Date::Manip has a UnixDate routine
that works like a specialized form sprintf
designed to handle dates. Pass it a Date::Manip date value. Using
Date::Manip in lieu of POSIX::strftime has the advantage of not
requiring a POSIX-compliant system.

use Date::Manip qw(UnixDate);
$STRING = UnixDate($DATE, $FORMAT);

3.8.3. Discussion

The simplest solution is built into Perl already: the
localtime function. In scalar context, it returns
the string formatted in a particular way:

Wed July 16 23:58:36 2003

This makes for simple code, although it restricts the format of the
string:

use Time::Local;
$time = timelocal(50, 45, 3, 18, 0, 73);
print "Scalar localtime gives: ", scalar(localtime($time)), "\n";
Scalar localtime gives: Thu Jan 18 03:45:50 1973

Of course, localtime requires the date and time in
Epoch seconds. The POSIX::strftime function takes
individual DMYMHS values plus a format and returns a string. The
format is similar to a printf format:
% directives specify fields in the output string.
A full list of these directives is available in your system''s
documentation for strftime. The
strftime function expects the individual values
representing the date and time to be in the same range as those
returned by localtime:

use POSIX qw(strftime);
use Time::Local;
$time = timelocal(50, 45, 3, 18, 0, 73);
print "strftime gives: ", strftime("%A %D", localtime($time)), "\n";
strftime gives: Thursday 01/18/73

All values are shown in their national representation when using
POSIX::strftime. So, if you run it in France, your program would
print "Sunday" as "Dimanche".
Be warned: Perl''s interface to the POSIX function
strftime assumes the date falls in the current
time zone.

If you don''t have access to POSIX''s
strftime function, there''s always the trusty
Date::Manip CPAN module, described in Recipe 3.6.

use Date::Manip qw(ParseDate UnixDate);
$date = ParseDate("18 Jan 1973, 3:45:50");
$datestr = UnixDate($date, "%a %b %e %H:%M:%S %z %Y");    # as scalar
print "Date::Manip gives: $datestr\n";
Date::Manip gives: Thu Jan 18 03:45:50 GMT 1973

3.8.4. See Also

The gmtime and localtime
functions in perlfunc(1) and Chapter 29 of
Programming Perl;
perllocale(1); your system''s
strftime(3) manpage; the documentation for the
POSIX module (also in Chapter 32 of Programming
Perl); the documentation for the CPAN module Date::Manip