I have coverage of an (long term) event taken from many different cameras.  I would like to combine all these sources.  But sorting the pictures by time does not help because the cameras were not synchronized.  And the timestamp to reality is all over the place.

I need a way to say something like:

For each picture taken by this camera make/model  (assuming that there were no repeat cameras)
     time created = time created + time adjustment


What is the best way to get this accomplished?  I already uploaded thousands of pictures to the server (it took me days!).  And I expect more people will add pictures of the event.  So I need a Piwigo / server side solution.

Thank you