I searched the group and didn't see anything that answered my question about date although I may have just not recognized it when I read it. The date constructor will throw exceptions if you use an invalid date: date d(2005,2,29); Throws an exception because there is no 29th of February in 2005. If one does the following: string ds("20050229T000000"); date d(from_iso_string(ds)); there is no exception and like localtime() and gmtime() it actually changes the date silently to 20050301. (ptime also does this.) Was this done intentionally perhaps to be consistent with localtime() etc although that begs the question of why there was an exception in the first case of date construction? Or perhaps I forgot to do something?