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