Why can't I remove time for tasks if I've set it up in a time-interval?
Did you remove the opportunity to remove a time for the tasks? At the moment if I have specified a time interval for a task I cannot remove it again - this is very annoying especially since the program automatically adds a task that you drag from one of your lists.
App:
Try to set the start time as 0:00. That's how you can remove the time.