I developed an android app to show the time for certain events so people there know what's coming and when. I bought one box, but it can't keep the correct time without being connected to the internet, and today, I tried multiple boxes at a local store and all of them failed to keep the time.
Also, I'm going to add a timer switch to allow the TV and the box to take a rest for 2 hours during the day, so it is a must when they turn on again, the time is correct.
I hope someone can help.
You need box with RTC support and i don't think there is certified Android TV device with RTC support.
For normal android box, check out UGOOS X series, it has RTC and looks easy to replace but it's expensive.