#!/usr/bin/perl -w

use strict;
use Date::Manip;

Date_Init("TZ=EST");  # target TZ

# use your filehandle here instead of DATA
while (my $date_anyTZ = <DATA>) {
    chomp $date_anyTZ;
    # get rid of '~' to make date parseable by Date::Manip
    $date_anyTZ =~ tr/~/ /;

    my $date_EST = UnixDate(ParseDate($date_anyTZ), "%Y-%m-%d %H:%M:%S %Z");

    printf "%-24s -->  %s\n", $date_anyTZ, $date_EST;
}

__DATA__
20050526~18:15:06 GMT
20040401~01:12:02 GMT
20060201~00:59:01 GMT
20060401~01:01:01 EST
20040201~10:10:01 -0600
20010901~04:23:05 -0400
20050526~18:15:06 GMT
20040401~01:12:02 GMT
20000101~00:59:01 -0200
19841223~04:22:06 MST