How does one set the RTC on the Pi 5 and also recover the time from it?

Question

All is in the subject line. I Have a Pi 5 but have been unable to find out how to use the RTC, there is a a dearth of information it seems.

cstanton · Answer

shabaz said: There's no RTC in the conventional sense 
 The Raspberry Pi 5 now has an RTC! 
 It's part of the Renesas / Dialog DA9091 PMIC. 
 It's supported by a 3v coin cell battery that connects to J5. This means we can now use " hwclock ".

javagoza · Answer

Please note that they do not recommend using a primary lithium cell for the RTC as it has a trickle charge circuit that is disabled by default. If enabled, this will kill the cell quickly. 
 According to the Raspberry Pi 5 documentation, it is possible to use the RTC module even without a connected battery. 
 https://www.raspberrypi.com/documentation/computers/raspberry-pi-5.html#real-time-clock-rtc

"The official battery part is a rechargeable lithium manganese coin cell, with a pre-fitted two-pin JST plug and an adhesive mounting pad. This is suitable for powering the Raspberry Pi 5 RTC when the main power supply for the board is disconnected, with a power-off current draw measuring in single-digit &micro;A, giving a retention time that can be measured in months."