Daylight Saving Timezones in PHP

I’ve long had issues working with timezones in PHP, especially when it comes to coping with Daylight Saving Time – the annoying inconsistent flexibility of shifting local times back and forward an hour for the Summer.

Recently, I’ve been using the putenv function to hardcode a timezone to an application, eg. for Greenwich Mean Time (GMT):

putenv('TZ=GMT');

The problem with this is it doesn’t cater for Summer timezones eg.BST (for British Summer Time).

I realised this morning that the value can actually be set to one of the many timezone locations rather than just a timezone code. Eg:

putenv(‘TZ=Europe/London’);

Using this, you can rely on the server to work out whether you are in Daylight Saving Time or not based on the specified location and current date.

I’ve implemented this on a CakePHP website (configured in config/bootstrap.php for those who use CakePHP) and it worked straight away.