Track days since things

I use the Countdown Days Since & Until app to track how long it’s been since health and beauty appointments so I know when it’s time to reschedule — I’m really bad at remembering to get my hair cut. I also use it to count down to vacations and anniversaries, occasionally opening the app to see how many weeks or days or even hours are left, and it’s nice to get a little surge of anticipation as the time between things shortens. After using the free version for years I finally paid $4.99 to unlock extras like adding photo backgrounds to certain events. Unfortunately, this particular app seems to be iOS‑only, but any simple “important dates” tracker would be useful. — CD