How to modify the release date of a cloned campaign?

I created a campaign that I intended to launch  last week, but had to delay. When I went back to make changes the previously scheduled launch date had expired and thus I wasn't able to approve and release. So, I decided to clone the campaign instead, which worked, but now the calendar is unavailable since the dates were in the past. So...the question is how do I modify the release schedule for a clone whose previous release date was in the past....

Thank you!