With Stampr you can add the date and time to the photos you take with your iPhone, the original photo and another with the mark will be saved on the reel. Right now it causes poor display in the image to which the data is added, but the creator will fix it soon.
You can configure it in the iPhone settings.
You can download it free on Cydia.
You need to have done the jailbreak.
I hate dates in photos, that's what EXIF data is for
It does not work for me, I do not get the date in the photos I take, at least when viewing it on the iPhone roll itself.