@purplelime Probably because you had the beta (TestFlight) version of the app before? If you go to your Mac system settings, search for "Subscription”, click on "Media and Purchases", and then “Manage" subscriptions, it will open the App Store to your list of subscriptions and Ivory should be in there with the correct date.

If that's the case, I wouldn't worry about the date in the app. It should update at some point.