Do I have to convert this column before the ST to a number, sort it during the ST as a number, and after the ST convert it back to the DD-MM-YYYY format?

Um no, just do a schwartzian-transform ;) 

@dates = map { $_->[0] }
sort {  $a->[1] <=> $b->[1] }
map { my $f = $_; s/\D//g; [ $f, $_ ] }
@dates;

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In reply to Re: Sorting dates with the Schwartzian Transform by Anonymous Monk
in thread Sorting dates with the Schwartzian Transform by Wobbel

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