RTC

The Core-1684JD4 development board has the "HYM8563" RTC (Real Time
Clock) chip, which can keep the clock running through the button
battery even when the development board is powered off.

The following are common RTC operations:

   # View RTC time
   $ sudo hwclock
   2022-08-09 10:53:15.268874+0800

   # View system time
   $date
   Tue Aug 9 10:57:03 CST 2022

   # Set system time to RTC time
   $ sudo hwclock -s

   # Save current system time to RTC
   $ sudo hwclock -w