Multiple alerts for ALL calendar events

I don't know if this is a setting in the Calendar app on the iPhone, or on the Watch app, but I have scoured the internet and I cannot figure out how to have more than 1 alert for ALL calendar events (yes I know you can have multiple alerts for a single specific event, but that's not what I'm asking).

So, for instance, I would like an alert to come to either my watch or iPhone 30 minutes before all events, as well as 15 minutes for all events.

Is there a way to do it?