In a fascinating article, Alex Komarov shares the design process that went into the development of his iPhone (and potential Apple Watch) app called “24 Hours”, a combined time zone calculator and 24 hour clock.

The app is available on the App store now, priced between 1 and 2 dollars/pounds/euros.

The problem:

our team and our clients are distributed across five continents. We have to deal with a half-dozen time zones on a daily basis, which can be a nightmarish experience: calls in the middle of the night, frustration, missed deadlines, broken communication, lost opportunities.

The solution (obvious, of course, to frequent visitors to this site):

We decided that using a 24 hour face is a fair trade-off: it’s not as familiar as a 12-hour clock face. People would have to get used to it, but they’d have a much easier way of telling and converting times once they do. We decided this was a fair trade-off.

The resulting app works well and looks good.

As for their Apple Watch app, it was rejected, because Apple don’t currently allow third-party watch faces:

Long story short: after a bunch of back and forth with the review team we decided to put Apple Watch version of our app on hold and released iOS-only version for the time being.

Although most of the built-in watch displays on the Apple Watch are either digital or analog 12-hour, there is in fact one 24 hour time display built-in — it’s the setting dial for the alarm clock:

It’s a well-known problem with the 12 hour dial that setting an alarm can be confusing and error-prone, particularly if you’re trying to set an alarm for a time more than 12 hours in the future.