MacWorks Plus II originally used a base year of 1988, so the clock could be set between 1988 and 2003. A modification is available to change the base year as required.
The Lisa will maintain time only as long as it is plugged in. When unplugged, the time will be lost immediately (unless the I/O board has working batteries which will maintain the time for a few hours at most).
That said, please ensure that you have removed the 4-AA NiCAD battery pack from the I/O board of your Lisa. If your Lisa still has one that hasn't yet leaked, you're very lucky! Remove it ASAP! Do this right now! When it leaks, it will destroy your I/O board[LisaFAQ] > [Hardware] > [The Lisa I/O Board] (Comment on this answer)