In a similar vein, check out reTerminal. Using battery powered devices with eInk screens that will last for months before needing a recharge. The screen is very customizable, and very easy to implement a calendar into.
And you can DIY reTerminal devices too. I already had a 7" eInk panel that I was able to convert with an ESP32 to eInk adapter.
New health care recommendation. Anytime you feel yourself getting sick, just tell yourself: