Find out when a trigger notification was shown to the user

[pke]

Scenario: A couple of notification are scheduled over some days. When each of them is opened I would like to find out on which date it was shown to the user. Since those or recurring notifications I can't store any date in them, as it would only be valid for the first notification shown to the user.

So does the OS inject some date into notifications, which is just not yet exposed in the notifee Event structure?