localtime takes a number of seconds since the epoch (usually 1st Jan 1970) and returns information about the date and time.

For more complex requirements, I recommend looking at DateTime.

#!/usr/bin/perl

use strict;
use warnings;
use DateTime;

# 1st Jan 2000
my $date = DateTime->new(year => 2000, month => 1, day => 1);

# Add a million seconds
$date->add(seconds => 1_000_000);

# See what you get - 2000-01-12T13:46:40
print $date;
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Update: Actually you can also do something similar using only modules from the standard distribution.

#!/usr/bin/perl

use strict;
use warnings;
use Time::Local;

# Warning: The parameters to timelocal can be a bit confusing
#          Read the documentation carefully
my $date = timelocal(0, 0 , 0, 1, 0, 100);

$date += 1_000_000;

print scalar localtime $date;
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