Backdating Task
 

I'm just starting out with OmniPlan and I'm importing tasks into a new project. However all the dates are starting today. I can't seem to move tasks, for example, three days before today. I've tried removing constraints but when I then try to move the task it just changes the constraint field and the task remains stubbornly at the date set by the import.

Other things I've tried:

1. Reset the system clock (really)
2. Change the task to complete to see if would move (nope)
3. Change the Set Current Editing Date to a week behind today

Nothing seems to work. I'm putting it down to user error but what am I doing wrong?

Thanks.