I'm new to Shotwell and imported my pictures. Some of the videos (apparently those I've shot with my smartphone) are now in a event dated to 1904, Jan 1st. I tried to edit the date, but the menu item (Photos->Adjust Time and Date) is unavailable for videos. Then I moved such a video into the correct event, but now the entire event is placed under 1904 and named "Fri Jan 1, 1904 - Sat Sep 11, 2010".
Unfortunately there's no way to set the date of a video in Shotwell 0.9.x.
But the good news is that this feature is already complete and will be in Shotwell 0.10!