I tried: dt = DateTime.DateTime(time.time()) dt.timeTime() and got just what I expected: 915677129.19 I then tried dt = DateTime.DateTime(0.0) dt.timeTime() and got a traceback: Traceback (innermost last): File "<stdin>", line 1, in ? File "DateTime/DateTime.py", line 874, in timeTime raise self.DateTimeError,'No time module compatible time to return' DateTimeError: No time module compatible time to return Surely 0.0 is a valid time module compatible time: time.gmtime(0.0) (1970, 1, 1, 0, 0, 0, 3, 1, 0) Can I not initialize a DateTime object to the Unix epoch? I tried several multiples of 10.0 and didn't avoid the traceback until I tried dt = DateTime.DateTime(100000.0) which is somewhat more than one day more recent than gmtime(0.0). There's apparently some magnitude-dependent interpretation of single numeric initializers, but the documentation file in the package is unclear on how it distinguishes between the two interpretations: A DateTime object is returned that represents either the gmt value of the time.time() float represented in the local machine's timezone, or that number of days after January 1, 1901. Note that the number of days after 1901 need to be expressed from the viewpoint of the local machine's timezone. A negative argument will yield a date-time value before 1901. While horsing around some more, I got some other strange behavior as well: >>> time.gmtime(24*60*60) (1970, 1, 2, 0, 0, 0, 4, 2, 0) >>> dt = DateTime.DateTime(24*60*60) >>> dt.timeTime() 86400 >>> dt = DateTime.DateTime(24*60*50) >>> dt.timeTime() 72000 >>> dt = DateTime.DateTime(24*60*40) >>> dt.timeTime() 57600 >>> dt = DateTime.DateTime(24*60*30.0) Traceback (innermost last): File "<stdin>", line 1, in ? File "DateTime/DateTime.py", line 513, in __init__ s=(_j-int(_j))*86400.0 OverflowError: float too large to convert >>> dt.timeTime() 57600 >>> dt = DateTime.DateTime(24*60*30) Traceback (innermost last): File "<stdin>", line 1, in ? File "DateTime/DateTime.py", line 513, in __init__ s=(_j-int(_j))*86400.0 OverflowError: float too large to convert Why would I be getting overflow errors as the numbers got smaller? Skip Montanaro | Mojam: "Uniting the World of Music" http://www.mojam.com/ skip@calendar.com | Musi-Cal: http://concerts.calendar.com/ 518-372-5583