Images.
The date and times of images can be checked by using an exif reader. This shows the image data at the time the picture was taken, aiding anyone who wants to verify a time/date location.
There are a couple of things to be aware of:
If date and time are incorrectly set on the camera that will be recorded as the event time, however most people tend to have date and time set reasonably accurately.
On some images, the processing/editing software may make the original exif data invisible.