use strict;
use warnings;
use Time::Local;
my %days;
@days{qw/0 1 2 3 4 5 6/} = qw/So Mo Di Mi Do Fr Sa/;

my $month = 2;
my $diff = timelocal(0,0,0,1,$month,2003-1900)-timelocal(0,0,0,1,$month-1,2003-1900);
my $tage = (localtime($diff))[7];
for (1..$tage) {
   print sprintf("%02d: ",$_),
         $days{(localtime(timelocal(0,0,0,$_,$month-1,2003-1900)))[6]},"\n";
}

01: Sa
02: So
03: Mo
04: Di
05: Mi
06: Do
07: Fr
08: Sa
09: So
10: Mo
11: Di
12: Mi
13: Do
14: Fr
15: Sa
16: So
17: Mo
18: Di
19: Mi
20: Do
21: Fr
22: Sa
23: So
24: Mo
25: Di
26: Mi
27: Do
28: Fr