DateTime changed, duh!

Yesterday evening, even before Zwiki bugday officially started, we had the first results. I had pestered Wu to get involved, even though he's pretty much busy with work. In the evening he tried out a little test script I needed for our problem with "last edit date". We noticed that on his server DateTime('2007-05-02 10:11:04') doesn't give the same result as on my machines. At first I had thought this to be OS dependant (all of my boxen live happily without "locale" support). But then I noticed that he was using Zope 2.10 and a little testing on my side and a bit of search revealed that Zope's DateTime() has indeed changed for 2.10.

Zwiki is falling exactly in the case that got fixed: We have date strings without time zone information. We use DateTime() to get the strings into DateTime() objects (so we can do time calculations) - but we so far expected the date and time to be interpreted as GMT or "Universal" time zone (aka UTC).

To fix this for all Zope versions we have two approaches: We can change the format for last_edit_time to include timezone information, providing upgrade methods. Or we can glue ' GMT+0' at the end of last_edit_time whereever we convert to a DateTime(). The first choice appears cleaner to me, but we've already changed that format a couple of times in the past, so I wonder what others have to say.