wouldn´t it be helpful to offer a funtion to give a personal or card date a "fulfilled" status (like the delete function already today). And after fulfilled the date is deleted, but a statusentry in the stream indicates the fulfillness of that date.
To be honest, I still do not understand the business problem you both are trying to solve. Maybe you could describe a specific situation where it will be clear what is missing or confusing in regards of the dates
Nicht optimal ist zudem, dass in der Timeline beim Klicken auf einen Terminknödel im Falle eines Kartendatums der Name der Karte erscheint (gut), bei einem sonstigen Datum aber nur der für den Termin vergebene Name (schlecht, ich muss erst die Karte öffnen um zu erfahren, zu welcher Karte der Termin gehört)
Could you be more specific? Can you explain what kind of business problem would this feature solve/improve?