A single module, monthdelta, is provided by the MonthDelta distribution. The monthdelta module includes a class, MonthDelta, and a function, monthmod(). MonthDelta enables easy month-related calculations with the standard Python date and datetime classes from the datetime module. monthmod() enables round-trip calculations among MonthDelta, date, datetime, and timedelta. Starting with version 2.3 (when the datetime module was added), MonthDelta supports all subsequent versions of Python from one codebase.
This library was originally developed as an enhancement to the C implementation of Python, to be included directly in the datetime module. That was not seen as a valuable addition to the standard library, so this "back-ported" Python module is the way to use this functionality.
Documentation is available, and the source is hosted at Bitbucket. Jess Austin is the author of MonthDelta. MonthDelta is distributed under the MIT license.