BUG: DataFrame[int] +/- datetime64
- [x] closes #28080 
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

this is technically a bug fix / api change? can you add a whatsnew note whatsnew note added, and green @jreback gentle ping; this is a blocker for the ops-perf fixing can you rebase :-< rebased+green Thanks!