what would cause the camera to stop retaining the date and time with new battery.

Cannon company said put in new battery. I did that an was no help.
It will take the date an time but when i turn it off it goes back to all zeros.

There is a lithium button battery that keeps the date and time going.
The battery must have exhausted and needs replacement.

Look for a small cover on the left hand side of the Screen. Pull it out, while the camera is off, and replace with a new battery of the same type and number and you will be OK.

The battery should be CR2016 or equivalent.

Thats the answer i got from Cannon tech support and i had tried a new battery as i said in the question. I just feel that there may be something else i might do to get it to retain the date. I did check the charge in both the old an new battery ab both were well charged.
The camera takes the date and the date works with the pictures taken as long as its not turned off. When its turned off an back on again the date returns to o1/01/1980.

Correction to my last post.
When the date is set correctly the an pictures taken they are downloaded with correct date.
when yhe camera is turned off and later turned back on the date returns to all zeros.
Any pictures taken while camera is indicating all zeros are downloaded 01/01/1980.

If Canon tech support gives the same answer as I do, it means we are on the correct track.

The next thing to do, on your part, is to check the battery terminals - the contact points. Worn out Lithium button batteries are noctorious for oozing out chemicals that corrode the contact points on the camera side. This would not allow current to go through and installing a new battery is as good as not installing any.

I used to scrap the corroded parts with a paper carving knife, sharp tiny blades like surgical instruments. If you don't have, a snapped hacksaw blade sharpened to an acute angle will do.

Scrap clean the contact points and probably you will be OK.
But make sure the "+" and "-" side of the battery is correctly mounted because I sometimes mount them wrongly for my computer motherboard.

I tried what you said bukit97. I could not see any corosion.I did clean it several times but still have no luck with date. I think you are probably right thinking it is not getting any power. I think it may ba a connection problem inside or something. I did recently have it repaired by cannon due to the sensor problem. Maybe something came loose after it was repaired. Cannon wants 85.00 to repair plus anything else they find. I think ill call your answer the best answer and just use it without a date. Maybe later i can afford another newer camera.
Thanks for youe help. I really do appreciate your time helping me with my camera problem.

Thanks bukit97 Ill try that.
I thought the $85 was too high also,
If i cant get it displaying a time an date then i can live with that until i can buy a new camera.
It still takes great pictures.
Thanks for the help, you definitely got the Best answer.

erm.. i tried all of those but it STILL doesnt work!! wats da PROBLEMO?!

I give up. I just press set each time i turn my camera on an that takes the error off the screan saying i need to set time an date. Then i just take all the pictures i want. Have to do that every time it is turned on. I dont have no date on my picyures but i got pictures. I changed the button battery 3 times. That aint the fix. An Cannon wants me to buy another Cannon. This did not start untill Cannon repaired my Factory Defect in my camera. Kinda like taking my truck to the shop with a bad starter and they send it back with a flat tire. I was Bragging up Cannon Pretty good but lately i been keeping my mouth shut in that reguard. Some day ill be able to afford another camera and Cannon now has a strike against them so not sure what brand ill buy. I do like the Cannon But aunt too happy with the flat tire if you get the picture. Little pun there, no date.
Taterpicker