Adjusting date and time

Hi.
I have a problem with adjusting date and time on my PowerShot A580. It's a completely new camera with new batteries, but it often asks to adjust data and time again (though I did it many times before it). When I adjust it, it stays in the memory for a few minutes (I can push the on/off button without needing to adjust date/time), but it asks adjusting again. I have no idea what the problem can be, because the machine doesn't always ask the adjusting.
Can anybody help me?
Thanks in advance!