Google calendar works fine on Win 10, and sync's perfectly with my Android phone Google calendar. Dead simple.
Should also sync with Windows calendar to do alerts on your computer.
Oh yes that would work, but I do not want to link the Google calendar to my computer, I just want something that will more or less pop up on a certain time of the month when I turn the computer on. thanks anyway
Do that on my W10 machine with Task Scheduler, a tiny script file to generate visual and audio reminder then command lines for the back-up program (I use FastCopy but you could presumably do the same with your back-up of choice).