dont keep date and time and off

"Denise, you should have a Coin-type lithium battery CR1220 on the circuit board of your camera. that is your RTC (Real Time Clock) battery and for as long as the battery works, your camera will retain it's settings. Including Time and date. When this battery does no longer work, you will lose the settings and have to reset it every time you start your camera. I would suggest to replace the battery. Hope this helps, good luck.

UPDATE 08/03/2018

Replacing the date battery PowerShot A510 and A520

Confirm that the camera is turned off.

Open the terminal cover and use your finger nail to pull out the battery holder.

Pull open the battery holder in the direction indicated by the arrow (1). Remove the battery by pulling it up in the direction indicated by the arrow (2).

Insert a new battery with the (-) side facing up.

Replace the battery holder back and close the terminal cover.

When the Date/Time menu appears, set the date and time."

"Hello, Not sure if all these questions have yet been answered, so I will try.

1) I have an A550 that also has been bugging me for months with the Reset Date & Time window when I power the unit on. Out of frustration one day, I pushed the menu button and the Reset Date & Time window closed. I was then able to use the camera without further issue. Keep in mind, you will need to repeat this process each time you turn the unit on.

2) In my camera, the CR1220 battery is located under the main battery access cover and inside a tiny lift out tab with the # CR1220 stamped on it.

Trust this helps."