Is there an RTC on Vivid Unit?

Yes, there is an RTC on Vivid Unit. It is actually integrated within the power supply management chip RK808.

There is no I2C interface for this RTC though, you can use hwclock command to access its data.

You can display the RTC with this command:

sudo hwclock --show

You can test the RTC with this command：

sudo hwclock --test

If you want the RTC to keep time when the device is not powered, you will need to connect a 3V battery to that small white connector.