It’s really very simple to convert times in different timezones using the following function.

function dateTimeConversion($datetime, 
$timezone="Europe/London") {
  $date = new DateTime($datetime, new DateTimeZone("UTC"));
  return $date->format("Y-m-d H:i:s");

As you can see, it takes 2 arguments, $datetime which is a time string and a $timezone which is a timezone to convert to.

A usage example would be:

echo dateTimeConversion("2012-05-01 17:09:58");