Hi Frances,
I know- I love my age on some planets!
I think this is the one I used (if memory serves correctly)
https://www.exploratorium.edu/explore/solar-system/age
I found it handy because it calculates the age for all the planets at once and shows when your next birthday will be- something the kids always get a great laugh out of!
I must try the one you’ve linked also- thank you.