I don't see 64 bits as a viable alternative; there just aren't any compilers out there that support a 64 bit integer, certainly we can't depend on it, and too much code likes to carry around a single quantity. The more I think about it, the more I think that if I am going to build a general library to handle dates and times, I'm not going to use a time_t as my canonical type, even extended to 64 bits. I need things like variable precision (e.g. my birthday should be clearly precise to the day, not the second, but some measurements have subsecond precision) and the ability to handle notions like "before". I don't see any reasonable way to implement it except using a character string as the canonical format - a char string in ISO format can do it pretty cleanly. Mark