First regarding the date and time. You need to replace the date and time battery in the camera. Here are some images on how to do it.
Regarding your camera download problem, have you tried a different known working USB cable or a different USB port in your computer? Have you upgraded either the computer OS or the iPhoto software recently?
If you have upgraded the OS for your computer, have you got the latest drivers for the camera installed in your computer? Here is a link, select the appropriate OS for your computer, http://search-au.canon.com.au/canon__au_....
Downloading and installing the Camera DC software should install the latest drivers available
Hopefully this is of some help.