use DateTime;
use DateTime::Format::Strptime;

my $parser = DateTime::Format::Strptime->new(
   pattern => '%a %b %d %T EST %Y', # see the docs for the patterns
   locale  => 'en_US', # to get the month and day names to parse
   time_zone => 'America/New_York',
);

my $now = DateTime->now(time_zone => 'America/New_York');
foreach (<DATA>) {
   my ($dt) = $_ =~ /^(.+?)\s:\s/;
   $dt = $parser->parse_datetime($dt); # turn the string into a datetime
   print $_
      if (($dt < $now) 
      and ($dt->add(days => 45) > $now))
}

__DATA__
Fri Dec 3 23:07:21 EST 2004 : Depth is : 234
Sat Dec 4 00:07:29 EST 2004 : Depth is : 123
Sun Dec 5 03:07:32 EST 2004 : Depth is : 144
Tue Feb 8 05:21:18 EST 2005 : Depth is : 11
Sat Feb 26 14:13:12 EST 2005 : Depth is : 4567
Fri Mar 11 17:09:38 EST 2005 : Depth is : 265
Sat Mar 12 07:07:27 EST 2005 : Depth is : 1654
Sat Mar 26 07:07:27 EST 2005 : Depth is : 1654