I don't think this is related to timedelta, I tried looking at this manual first: http://docs.python.org/2/library/datetime.html#timedelta-objects
Then I tried something obvious:
>>> int = 063
>>> int
51
It looks like a leading in a numeric type is understood as a octal value to python. Also, if it starts with 0x its considered a hex which makes sense. The leading 0 really threw me off but it is also answered in this thread: