I might be old-fashioned, but I think Time::Piece is overkill for this task:

sub usage {
    my $err = shift and select STDERR;
    say "usage: $0 YYYYMMDD [YYYYMMDD]";
    exit $err;
    } # usage

use Time::Local "timelocal_posix";

my $from = shift or usage (1);
my $to   = shift || do {
    my @d = localtime; (($d[5] + 1900) * 100 + $d[4] + 1) * 100 + $d[3
+] };

my ($y, $m, $d, $Y, $M, $D) = "$from:$to" =~ m{
    ([1-9][0-9]{3}) -? (0[1-9]|1[0-2]) -? (0[1-9]|[12][0-9]|3[01]) :
    ([1-9][0-9]{3}) -? (0[1-9]|1[0-2]) -? (0[1-9]|[12][0-9]|3[01])
    }x or usage (1);

$from gt $to and usage (1);

my @w = qw( Sun Mon Tue Wed Thu Fri Sat );
$to   = timelocal_posix (0, 0, 13, $D, $M - 1, $Y - 1900);

if ($d >  1) { $d = 1; $m++; }
if ($m > 12) { $m = 1; $y++; }

while (($from = timelocal_posix (0, 0, 12, $d, $m - 1, $y - 1900)) < $
+to) {
    my @d = localtime ($from);
    printf "%s %4d-%02d-%02d\n", $w[$d[6]], $d[5] + 1900, $d[4] + 1, $
+d[3];
    if (++$m > 12) { $m = 1; $y++; }
    }
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