Retevis RT73 Configuration and Firmware at the time this was written..
|Version Date||Nov 27 2020|
From the Radio Menu, the "Appendix" selection will show several sub-menus including one to set the date and time.
The rotary menu button can be used to move to the fields that you want to change under date, or time. You use the microphone keypad (the number keys) to actually set the value.