Not sure you will gain very much, but you could reduce these three regular expressions: 
$line[4] =~ s/:/\//;
($month) = $line[4] =~ m/(\d+)\/\d+/;
($day) = $line[4] =~ m/\d+\/(\d+)/;

[download]
to only one: 
my (month, $day) = $line[4]  =~ m/(\d+):(\d+)/;

[download]
But the thing that you should really do to start with is to profile your code, using for example http://search.cpan.org/~timb/Devel-NYTProf-5.06/lib/Devel/NYTProf.pm. Then only you will know where your program is spending time.

In reply to Re: DateTime speed improvement - suggestion by Laurent_R
in thread DateTime speed improvement - suggestion by ler224

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