In the legacy events for behavioral app events, you were able to refine them by date (ie. less than 2 weeks ago). I noticed that in the new model for passing custom app events, this feature is no longer available. We've already started re-building our app events to the new model but did not pass over a timestamp because we thought this feature would be there.
This feature was very helpful when using Legacy app events and I'd love to see it introduced in the new custom app event model.