Scott,

> Can you explain how to do this with some code?  I looked for real-time
> clock and world cycle on the swiki but didn't come up with anything
> useful.

"Date today" and "Time now" will do the trick. Since the internal clock
of the PDA won't sleep while the PDA is sleeping you should be able to
do something like:

PDAWorld>>initialize
	lastDate := Date today. "might sleep for more than a day"
	lastTime := Time now.

PDAWorld>>doOneCycle
	| nowDate nowTime |
	nowDate := Date today.
	nowTime := Time now.
	(lastDate ~= nowDate or:[nowTime seconds > (lastTime seconds
+5)])
		ifTrue:["redraw everything"].
	"..."

Cheers,
  - Andreas