Sometime back I got a multiple timer program for my tablet device and seemed to find some new use for it every month or so. Here's a simple and clear method for maintaining not just a few but LOTS of timers:
http://www.spacejock.com/yTimer2.html
https://www.softpedia.com/get/PORTABLE- ... able.shtml
Can also do some basic automation like launching a program at timer end.
From SpaceJock who's also been mentioned here on the site for yWriter: viewtopic.php?p=5703#p5703
Status: Untested
The closest option outside of a list of timers that I was able to find on the site was DateReminder https://www.portablefreeware.com/index.php?id=831 (providing a list of dates).