use 5.010;

use warnings;
use strict;

use DateTime::Event::ICal;
use DateTime;

my $dt = DateTime::Event::ICal->recur(
    dtstart  => DateTime->now,
    freq     => 'monthly',
    byday    => [ "-1fr" ],
    byhour   => [ 15 ],
    byminute => [ 0 ],
    bysecond => [ 0 ],
);

say $dt->next->epoch();