I know. They did it to me after posting my reply. Downvoted almost instantly ;-)

Nevertheless. If it's just a small routine, I prefer to use my own algorithm in favour of using just another library that need to be installed and that I need to learn to handle ;-)

If someone using my module wants reliable handling of dates then they are advised to install a reliable date handling module

That's fair and if you can live with it... okay for me :-)

Maybe I will get hanged. I will try and write YADCM (Yet Another Date Calculation Module).