Time zone conversion with PHP

I do not like time zones. They’ve been a fairly regular pain point in my career, especially early on. There was even a time when I built something and totally forgot that time zones existed and well, it was a mess.

For the most part, time zones don’t cause me much bother anymore. At this point, I always store everything in a data store in Coordinated Universal Time, and then convert things to local time zones as necessary.

One such scenario came up recently for me, on a project that’s written in PHP.

While I do maintain some things that run on PHP, I’d say that my muscle memory for things like time zone conversion have waned considerably as I’ve spend the better part of the last decade slinging Node.js professionally.

Of course PHP can handle the job, thanks to the DateTime and DateTimeZone classes.

So let’s say you have a date/time string that’s in UTC. You can create a new DateTimeZone object for UTC and whatever other time zone you’d like. Using those, you can create a new DateTime object, that can then have the time zone set to the new time zone.

Putting it all together, it looks something like this:

$old_tz = new DateTimeZone('UTC');
$new_tz = new DateTimeZone('America/Chicago');

$old_time = new DateTime('2023-03-19 03:30:00', $old_tz);

$old_time->setTimezone($new_tz);
$new_time = $old_time->format('Y-m-d H:i:s');

var_dump($new_time); // 2023-03-18 22:30:00

Of course, you can adjust the time zone names as you see fit.