Arduino zero real time clock battery

Hello I'm trying to get some advice on trying to keep the Arduino zero board alive when the power is unplugged. I'm running the RTC real time clock onboard the arduino zero board. Well It's a adafruit tinker board small one. It runs the Arduino zero bootloader. The problem I'm having is that if the power is removed then the real time clock is gone. Would there be a easy way of keeping it going to keep the clock running somehow?


Use an external RTC, they are inexpensive and use a small battery that will last for years. Then when the power goes off and you take a two month vacation when you come back and turn it on it will be correct.

I don't see any VBAT pin on the SAMD21 so you can't technically remove the power to the chip and expect the built-in RTC peripheral to work.

The RTC in the Zero allows you to wake-up the CPU from a very deep sleep asynchronously. It works pretty well as the SAMD21 has an accurate internal 32768 clock.