3.8. Printing a Date

Problem

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

Solution

Simply call localtime or gmtime in scalar context, which takes an Epoch second value and returns a string of the form Tue May 26 05:15:20 1998 :

$STRING = localtime($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);

Discussion

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





Sun Sep 21 15:33:36 1997



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 a set of individual DMYMHS values and 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 . strftime expects the individual values representing the date and time to be the same range as the values 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 always converts the date, assuming that it 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







See Also

The gmtime and localtime functions in perlfunc (1) and Chapter 3 of Programming Perl ; perllocale (1); your system's strftime (3) manpage; the documentation for the POSIX module (also in Chapter 7 of Programming Perl ); the documentation for the CPAN module Date::Manip