I believe date can not be removed.But you can crop the video or use a virtualdub filter to blur that anoying timestamp.For both processes you must reencode the video.
Here's a website with some usefull tools,mods,hints for keyfob camera ->
http://chucklohr.com/808/
Virtualdub pluggin ->
http://www.aircommandrockets.com/md80clone.htm