Hello, I been having this problem for a while in many moodle versions. When I used the core H5P activities, the blue ones, and in settings I set the "Set reminder in Timeline" in completion conditions, it works and the date and time  appears eventually in the calendar. But if for some reason I change the date, the new date won't apper on the calendar but the previous date, I wait if it would change but the system never updates the calendar, it keeps showing the old date not the new one. This is very fruatrating because it keeps sending notifications to students for the wrong dates. At this moment I am using Moodle 4.4.2 version in a VPS.