When you submit an app to Apple for review, you have the option to set a specific release date. You can only specify a day, not a time, however. So at what time on the specific date will the app actually be released? At midnight GMT? When the folks in Cupertino come to the office? At a random time during the day? Will the app appear in all App Stores in all time zones at the same time?

It turns out that an app with a specified availability date appears on an international App Store roughly at midnight in the store’s local time zone. So New Zealand will have a 16-hour head start on the United States.

To illustrate this, let me document some tweets from the day the Tapbots released Tweetbot recently.

At midnight (local time), Tweetbot appears on the App Store New Zealand. Tweetbot developer Paul Haddad begins to wonder what’s up. Federico Viticci has the explanation:

F*ckin' Timezones. How do they work? @tapbot_paul tapbot_paul

@tapbot_paul The App Store's timezone system sucks. App is rolling out at 12AM internationally. @viticci Federico Viticci

@viticci I figured that might happen but for some reason thought it would start at midnight GMT @tapbot_paul tapbot_paul

@tapbot_paul Nah. It always begins in Japan and New Zealand, then slowly rolls out basing on timezone. @viticci Federico Viticci

A few hours later, Tweetbot says Hello to Japan as it is released on the Japanese App Store. Meanwhile, Paul has to answer lots of questions from users for whom Tweetbot is not yet available:

Konichiwa! @tweetbot Tweetbot for iPhone

For folks upset Tweetbot isn't available in your store yet blame Sandford Fleming and the International Date Line. Or Apple, I suppose. @tapbot_paul tapbot_paul

Just after 11 pm GMT (midnight in the UK and 1 am in Western Europe), Tweetbot has appeared on the European App Stores.

Looks like its midnight in Europe and the UK stores. Only US/Canada/World left. @tapbot_paul tapbot_paul

US users still have to wait:

fwdr.org/yu8v Can somebody please tell me why the FUCK Tweetbots isn't showing up for me no matter what I do? Kthx. cc: @tapbot_paul @rockets Buzz Bellamonté

@rockets not out in the US yet, you have to wait a few more hours. @tapbot_paul tapbot_paul

Finally, 16 hours after New Zealand, Tweetbot goes live on the US App Store: