Hi. I've used the date_time I/O using facets and found it too complicated. The thing that bothers me is that I need to use a facet to specify the format string (e.g "HH:MM:SS"). This is burdensome. IMO, using facets is fine for defining things which are really locale-related (and are mostly constant during the process lifetime) such as the month names in the local language. The format is not such a property and can often change throughout the application, and as such is much better handled using an I/O manipulator: cout << time_format("HH:MM:SS") << my_ptime << endl; or if this is impossible, then cout << time_io(my_ptime, "HH:MM:SS") << endl; which surely is possible. I think of specifying the format string as similar to specifying the printing precision of a float, or specifying that an integer should be printed as hex. These are provided as manipulators without the complexity of facets (which most users, including me, know very little about). BTW, this is not my original idea. I saw it in a post (don't remember by whom) in this mailing list a few months ago. Thanks, Yuval