With conditional activities enabled some activities have two sets of available to/from controls. One from conditional activities and one from the activity itself. See the attached screenshot.
Fixing this will involve the upgrade migrating the data in, for example, timeavailablefrom and timeavailableto in the data table into a conditional activity condition. If any activities have available from/to set the upgrade will need to enable conditional activities. Then the UI elements in the activity settings forms can be removed.
Activities that have this problem:
Workshop is a problem as it has two sets of dates. Open for submissions and open for assessment.