Right now, the only supported trigger for O365 calendar is "Meeting is about to start (in 15 minutes)". With more options for this trigger, a lot more scenarios would be possible. For instance, you could make a recipe for late-night across-the-world business calls: "If event is after 5:00 pm, send me a reminder / ring my home phone / flash the lights / etc." At the very least, I'd like to see "event is after or before <specific time>".