You know when you stumble upon a tiny aspect of an experience with a product or service that is so delightful or so annoying that you instantly turn around to point it out to the person next to you? This (hopefully) series will highlight some of them and thus give a little shout out to some designer who has clearly put some thought into the user experience of their product – or hasn’t.

In iCal on Mac OS X (10.6 Snow Leopard in this case), try to create an event sometime between 2am and 3am Australian Eastern Standard Time on Sunday 4 October. Regardless of whether you try to drag and drop it there or use the (dreadful – but that’s for another post) editing interface, iCal won’t let you. Why? Because the hour from 2am to 3am does not exist on that day, thanks to Daylight Saving Time.

Strangely, when you create an event between 2am and 3am on 4 April 2010, iCal does not ask you whether you want that to be old time or new time.