Hot Koehls

The more you know, the more you don’t know

This content is a little crusty, having been with me through 3 separate platform changes. Formatting may be rough, and I am slightly less stupid today than when I wrote it.
24 Nov 2009

Run your servers without timezone offsets

I recently made the decision to store times on Fwd:Vault systems in Greenwich Mean Time, or GMT. I decided to do this because I have time-sensitive events happening along several dimensions. Email coming into the system has several timestamps associated with it: the user’s initial delivery, relay from their mail server, and receipt by the Fwd:Vault mail server. Payment receipts come into Fwd:Vault from our billing provider, which gets stored in my system and made available to the user. Up until now, my server time was set for the US Eastern, where both I and the server physically reside. Then I started building the code to display local time based on a user’s selected timezone. Ugh. Here’s the problem: displaying local time requires at least one time conversion, from server time to the user’s timezone. If the time is initially set to anything other than no-offset GMT, you have two calculations to do, from the server timezone to GMT, then GMT to user timezone. You can do it, of course, but who really wants to write even more code? Now add to this equation the fact that most data-delivery systems have settled on sending time data in GMT. A very good practice, to be sure, but presents the need to do another timezone conversion when the data come into your systems. Going back to my example, I had to convert payment times from GMT to US Eastern before dropping them into my database. Finally, add to the mix the potential for time data coming in from more than one source with more than one offset. Again back to my case, payment data is GMT, as is the Twitter feed I store and display on the site. Meanwhile, email was set to US Eastern. This matched the server and MySQL database where all the data ends up residing, so I was still looking at just one time conversion. But what happens down the road, when my server configuration changes, or I move to another timezone? Tying this information to me makes as much sense as tying it to any one of my users. It’s the same rationale that data service providers use when delivering GMT time data, it applies to me, and it applies to you too. I’m just too lazy to try and keep all that timezone switching straight in my head. If you find yourself in the same scenario, save your sanity and your future support efforts. If you run a website that (a) displays time-sensitive data, and (b) allows users to create an account, you really owe it to everyone involved to store time in a neutral fashion and adjust time displays according to the user’s selected timezone.

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