It's a question that someone asked on the site but also I had wondered if this was possible. eg.
"Alexa turn the living room light off in 20 minutes" or " turn the living room light off at 10pm".
I didn't have any joy yet it shouldn't really be a problem since you can ask Alexa to set an alarm which is very similar.
I'd have thought it would have been possible to invoke any skill at a specific time but what do I know.
It would be very useful though, maybe someone knows of a way?