DateTime is one of these formats:
All well and good, but is this level of detail really needed? Its scarily long, complex etc.?
2003-07-10T15:59:60-08:00 is valid according to jing,
I'd prefer something simpler, at least as a slow time option, e.g. 2003-07-10
The W3CDTF (WWW Consortium DateTime Format) is a simple subset of ISO 8601 and can be shortened down to just the year (if you're a really lazy blogger). It's used in various existing specs, notably RSS 1.0 (from DublinCore). Both of the above examples are valid.
[MarkDrago] I'd prefer we just use unix time. It's always UTC and simple to localize and parse into parts.