To change the start date, just follow these steps:

1. Click Marketing, then click Drip Campaigns
2. Under "Active Programs", find the program you want to change. To the right of the program, you will see the number of events, then the number of clients assigned to that program. Click on the number of clients.
3. Check the boxes in front of the clients you want to change (or hit Select All). Click the "Change Start Date" button.
4. Look at the very bottom of the page. Select the new start date using the calendar icon, and hit Save. That's it!

NOTE: If you have a long list of clients, the "Change Start Date" button does not appear to do anything. You must scroll to the very bottom of the page.