I have not used the BE in far too long, but have used autoexec.bas to load the current date and time from a RTC connected to the BE via I2C. Then it updates the system time & prints the current time and date onscreen. I'll try and dig up the code today if it'd be of interest.
EDIT:
Check out the following github link to two files, AUTOEXEC.BAS & SETRTC.BAS
(I can't figure out how to post code here directly without formatting issues, does anyone have any pointers?)
https://github.com/peek82/BASIC_Engine_Software/tree/main/RTC_via_I2C
SETRTC.BAS allows you to set (program) the time into the RTC. Just update the current system time/date as accurately as possible first, because it pulls this data when setting the RTC.
AUTOEXEC.BAS will load the current time from the RTC and set the system clock accordingly.