Day of Week rule trigger

Any way to trigger a rule based on day of week?

Not sure if this is exactly what you are asking, but you can use the day of the week as a condition in a rule.
 
For example, this would turn on output 100 every Monday.
 
WHENEVER THE TIME IS 12:00AM
 
AND THE DAY(S) OF THE WEEK IS/ARE -M-----
 
THEN TURN OUTPUT 100 ON FOR 24 HRS

There's lots of conditionals that can be driven based off day of week, time windowns, etc.

The more accurate question is what are you attempting to do?