Hm, I thought that databases have their own date/time types? Aren't these used?
At C level, interfacing is usually done using structs (ISO SQL/CLI defines these).
Ah, there's another requirement that we (or at least I) almost forgot. There should be an efficient C-level interface for the abstract date/time type.
This stuff is hairier than it seems! I think the main tension is between improving upon the Unix time_t type, and improving upon the Unix "struct tm" type. Improving upon time_t could mean to extend the range beyond 1970-2038, and/or extend the precision to milliseconds or microseconds. Improving upon struct tm is hard (it has all the necessary fields and no others), unless you want to add operations (just add methods) or make the representation more compact (several of the fields can be packed in 4-6 bits each). A third dimension might be to provide better date/time arithmetic, but I'm not sure if there's much of a market for that, given all the fuzzy semantics (leap seconds, differences across DST changes, timezones).
--Guido van Rossum (home page: http://www.python.org/~guido/)