my @sundays = ([]);
my @date = (2005, 1, 1);
$date[2]++ while Day_Of_Week(@date) != 7;

DATE: {
    push @sundays, \@date;
    @date = Add_Delta_Days( @date, 7 );
    last if $date[0] == 2006;
    redo DATE;
}

# Now, $sundays[1] == ( 2005, 1, 2 )
# $sundays[2] == (2005, 1, 9 )
# etc.