How do I convert a date/time to epoch time (unix time/seconds since 1970) in Perl?

Question

Given a date/time as an array of (year, month, day, hour, minute, second), how would you convert it to epoch time, i.e., the number of seconds since 1970-01-01 00:00:00 GMT?

Answer 1

Get Date::Manip from CPAN, then:

use Date::Manip;
$string = '18-Sep-2008 20:09'; # or a wide range of other date formats
$unix_time = UnixDate( ParseDate($string), "%s" );

edit:

Date::Manip is big and slow, but very flexible in parsing, and it's pure perl. Use it if you're in a hurry when you're writing code, and you know you won't be in a hurry when you're running it.

e.g. Use it to parse command line options once on start-up, but don't use it parsing large amounts of data on a busy web server.

See the authors comments.

(Thanks to the author of the first comment below)

Answer 2

$ENV{TZ}="GMT";
POSIX::tzset();
$time = POSIX::mktime($s,$m,$h,$d,$mo-1,$y-1900);

Answer 3

I'm using a very old O/S that I don't dare install libraries onto, so here's what I use;

%MonthMatrix=("Jan",0,"Feb",31,"Mar",59,"Apr",90,"May",120,"Jun",151,"Jul",181,"Aug",212,"Sep",243,"Oct",273,"Nov",304,"Dec",334);
$LeapYearCount=int($YearFourDigits/4);
$EpochDayNumber=$MonthMatrix{$MonthThreeLetters};
if ($LeapYearCount==($YearFourDigits/4)) { if ($EpochDayNumber<32) { $EpochDayNumber--; }}
$EpochDayNumber=($YearFourDigits-1970)*365+$LeapYearCount+$EpochDayNumber+$DayAsNumber-493;
$TimeOfDaySeconds=($HourAsNumber*3600)+($MinutesAsNumber*60)+$SecondsAsNumber;
$ActualEpochTime=($EpochDayNumber*86400)+$TimeOfDaySeconds;

The input variables are;

$MonthThreeLetters
$DayAsNumber
$YearFourDigits
$HourAsNumber
$MinutesAsNumber
$SecondsAsNumber

...which should be self-explanatory.

The input variables, of course, assume GMT (UTC). The output variable is "$ActualEpochTime". (Often, I only need $EpochDayNumber, so that's why that otherwise superfluous variable sits on its own.)

I've used this formula for years with nary an error.

Answer 4

To parse a date, look at Date::Parse in CPAN.

Answer 5

I know this is an old question, but thought I would offer another answer.

Time::Piece is core as of Perl 5.9.5

This allows parsing of time in arbitrary formats via the strptime method.

e.g.:

my $t = Time::Piece->strptime("Sunday 3rd Nov, 1943",
                              "%A %drd %b, %Y");

The useful part is - because it's an overloaded object, you can use it for numeric comparisons.

e.g.

if ( $t < time() ) { #do something }

Or if you access it in a string context:

print $t,"\n"; 

You get:

Wed Nov  3 00:00:00 1943

There's a bunch of accessor methods that allow for some assorted other useful time based transforms. https://metacpan.org/pod/Time::Piece

Answer 6

There are many Date manipulation modules on CPAN. My particular favourite is DateTime and you can use the strptime modules to parse dates in arbitrary formats. There are also many DateTime::Format modules on CPAN for handling specialised date formats, but strptime is the most generic.