$ use DateTime $ my $d = DateTime->new(year => 1974, month => 11, day => 1, hour => 0, minute => 0, second => 0, time_zone => 'UTC') 1974-11-01T00:00:00 $ $d->clone->add(seconds => 0x40_E3_7F_D1) 2009-05-01T03:06:36 $ $d->clone->add(seconds => 0x40_E3_7F_D2) 2009-05-01T03:06:37 $ $d->clone->add(seconds => 0x40_E3_7F_D9) 2009-05-01T03:06:44 $ $d->clone->add(seconds => 0x40_E3_7F_E0) 2009-05-01T03:06:51