I'm not sure of your exact model, but here's how to do it on the cheapo 808 keychain cam:
Use a USB cable to plug the camera into a PC. Once the camera is detected, open it up and look for a configuration file. They all have different names, but importantly, the file extension will be .txt
Open that text file and find the parameter for date/time. You should be able to type in the current date and time. Save the file, and you should be good to go.
Alternatively, the date/time parameter will have a binary modifier next to it's line item in the text file. Date stamp "on" will be a 1, date stamp off would be "0". Changing that 1 to a 0 will effectively turn off the date and time stamp and you won't have to see it anymore. Don't forget to save the text file when you're done editing itz or the changes won't take.
Hope this helps.