use strict;
use warnings;

sub myGetTime {
    my($timezone) = shift;
    $timezone = 0 unless $timezone;
    # convert to seconds
    $timezone = $timezone * 3600 if ($timezone);
    my($time) = time + $timezone;
    return (gmtime($time));
}

print "Local  : " . localtime(time) . "\n";
print "London : " . &myGetTime      . "\n";
print "Houston: " . &myGetTime(-5)  . "\n";
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Your example works fine if you want to add or subtract hours from the current local time. However, the date the original question is not accessible from the time call. It must be parsed, converted to an apropriate timestamp value and de-timezoned before you can start using localtime or gmtime to manipulate it. And what if the output format the person wants isn't what gmtime or localtime produces? It must then be manipulated again into the proper format. All these functions are provided for you by the Date and Time modules.