Learn how to work with date and time values using Python's datetime library, and how to avoid some of the gotchas and pitfalls of the datetime datatype.

but the python datetime.time class doesn't seem to have defined arithmetic operators, nor does the datetime.timedelta. if there are methods for this, that's not obvious to me either: Code: ...

This post explains what a Python module is and how to use it to drastically extend the capabiltiies of your code. Plus: how to make your own!