Your question is unclear. I think you're asking for the last Sunday before the first day of the current month. 

use DateTime qw( );

my $dt = DateTime->today();
$dt->set_day(1);
$dt->subtract( days => $dt->day_of_week() );

print($dt->ymd(), "\n");

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DateTime

In reply to Re: Calculating latest 'Sunday' date on the first of the month by ikegami
in thread Calculating latest 'Sunday' date on the first of the month by Cicatrix

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