No Setup Date on imported sites -- How to modify?

When I migrated sites from Ensim to Cpanel, no "setup" dates were put on the sites -- all say "unknown". I didn't notice this until I downloaded a trial version of WHMAUTOPILOT and tried to import sites. It would not import the sites I had transferred from the Ensim box -- only the new sites I had created since the migration. The Whmautopilot creator said it could not import sites that did not have a setup date and suggested I do a global date change on the sites.

Can someone tell me how to do this?

Many thanks ....