As this is iOS only, it would really benefit from "Log in with Apple"!
As with all social networks: People only use it if their friends are using it, whom intern have the same problem. This would be great if it would incoroprate automatic recaps of post on other platforms, if a Contact does not have sundayy.
Autmaticly generate A summary from their instagram / facebook for example.
Niantic (The Company behind Pokemon Go and Ingress) would do something similar for events in Ingress:
They had a "measurement window", in which they would look at the state of the gameboard in a certain city and count stats (details irrelevant for the story here). The measurement window was 10 minutes long, but they would look randomly at one specific second and count the state at that second. Before each measurement window they would post a SHA hash on their twitter account, and release the string that lead to it afterwards (which was a bunch of garbage and a time like this: "52o5dfeis(})5eidfjsdkdbn 10:03:20 huner54652&e") Worked great for that proof :)