gistfile1.txt

# As rotations get later, distance gets longer:
# 7 rotations are latest, 6 daily
# 10 rotations are latest, 6 daily and 3 weekly (a full month of coverage)
# 15 rotations are latest, 6 daily, 3 weekly, and 5 monthly (6 full months)
use DateTime;
my $MAX_DAYS  = 7;
my $MAX_WEEKS = 4;

sub get_rotation_dates {
    my ($dt_today, $num) = @_;
    my $dt      = $dt_today->clone->truncate( to => "day" );
    my $dt_sun;
    my $dt_first_sun;
    my @dates = ();

    # 1 is "latest"
    $num--;

    # 2-7 are "daily"
    my $days = 0;
    while ( $num-- >= 0 && ++$days <= $MAX_DAYS - 1 ) {
        $dt->subtract( days => 1 );
        if ( $dt->day_name eq "Sunday" ) {
            $dt_sun = $dt->clone;
        }
        push @dates, $dt->ymd;
    }

    # 8-11 are "weekly"
    $dt = $dt_sun->clone;
    my $weeks = 0;
    while ( $num-- >= 0 && ++$weeks <= $MAX_WEEKS ) {
        $dt->subtract( weeks => 1 );
        if ( $dt->day <= 6 ) {
            $dt_first_sun = $dt->clone;
        }
        push @dates, $dt->ymd;
    }

    # 12+ are "monthly"
    $dt = $dt_first_sun->clone;
    while ( $num-- >= 0 ) {
        $dt->subtract( weeks => 4 );
        push @dates, $dt->ymd;
    }

    return @dates;
} ## end sub get_rotation_dates

$, = "\n";
my $dt = DateTime->now->truncate( to => "day" )->subtract( days => 3 );
print get_rotation_dates( $dt, 15 );
print "\n\n";
$dt->add( weeks => 3, days => 5 );
print get_rotation_dates( $dt, 15 );
print "\n\n";