Heads up - if your MM+ is recent enough, it might already have the required RTC hardware/wiring: https://old.reddit.com/r/MiyooMini/comments/1ceibjj/rtc_on_the_miyoo_mini_stepbystep_guide/
I was pleasantly surprised to find mine did, and after following the guide to enable it, it works a treat.
Ah bummer, sorry to hear