You could use an ICal expression:

use strict;
use DateTime::Format::ICal;

my $s = DateTime::Format::ICal->parse_recurrence( 
    recurrence => "freq=yearly;byweekno=10,20,30;wkst=SU" );

my $dt = DateTime->today;

print "Next occurrence: ", $s->next( $dt )->datetime, "\n";

# Next occurrence: 2005-03-11T00:00:00
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