Use a CR2032 replacement battery.
Enter the datetime value in the form MMDDHHMMYYYY.
For example:
-> set /SP/clock datetime=091214052012
-> show /SP/clock
/SP/clock
Targets:
Properties:
datetime = Wed Sep 12 14:05:20 2012
timezone = PDT (PST8PDT)
uptime = 15 days, 02:36:54
usentpserver = disabled