ISO8601

In my opinion, the use of timestamps for the representation of dates in Drupal core is problematic. It is fine for recording all events that happen now, and it is even fine for recording historical events, as long as they happened 1970 or later. They are utterly useless if you want to make a geneology site.

More disturbingly, the event module also relies on timestamps for representation of events. As far as I can tell, this is a huge limitation. The CCK date field uses the ISO 8601 standard which saves times as as string: 20060610T20:47:48+01:00. While there are lots of arguments about how the data should be persisted in the database, to me, it is clear that the ISO 8601 string is ideal for representing the date in Drupal code (unless you're doing archeology, then I've got no idea what you do with BC dates).