How to Filter by Time

If you would only like facebook access from 2pm to 4pm every day (14-16 in 24-hour notation), here is how you could do it with Pluckeye:

pluck add "Sometimes 14-16 Allow facebook.com"

Or, more stringently:

pluck add "Sometimes 0-14&16-24 Block facebook.com"

See eg.plu for complete rule syntax.