TST: add tests for using .at() with DateTime indexes
- [x] closes #29709 
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.


added the tests described in issue #29709 but I feel like more around this subject could be written. let me know what you think! thank you for your time

Hello @nealxm! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2022-08-31 02:15:58 UTC Hi Patrick, thanks so much for the feedback hopefully this is better. Just aside, I did not ignore your note on creating `df` just with passing `data=1` I just removed the the explicit column names to make comparing two full data frames a bit easier so the dimensions were no longer given.  hello! I never left a comment after I fixed what your comments were referring to, just wanted to update you that I took care of it.  Thanks @nealxm 