Dates, paths, and the standard library

Most of what you need already ships with Python

Datetimes come in naive and aware flavours, and mixing them raises an error at the worst moment. Store and compute in UTC, convert to a local zone only for display, and the entire category of bug disappears.

Path objects replace string concatenation for filesystem work. Joining, extension changes, and existence checks all become methods, and the result is correct on every platform.

Before adding a dependency, check the standard library. Grouping, permutations, temporary files, and configuration parsing are all already there.