BUG: Fix index bug due to parse_time_string GH24091
- [x] closes #24091
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

In Issue #24091 I detailed the root cause of the bug, and implemented the @toobaz suggestion.

I added a single line to test this case in the existing test, ran the full UT suite, checked the linting, and added a whatsnew (I added the whatsnew in the other category, as It wasn't clear where it belonged).


