Remove datestamp (watermark) from videos
Use ffmpeg (download a static build for your operating system) and its delogo filter, which will try to cover up a logo or watermark by interpolating neighboring pixels.

ffmpeg -i input.mp4 -vf "delogo=x=100:y=100:w=150:h=20" output.mp4


Here, x and y specify the top left coordinates of the “masking” rectangle, and w/h specify its size. You can add the show=1 option to help locate that rectangle.

If you want to play with the filter values, you can use ffplay to directly show the result:

ffplay -f lavfi -i "movie=input.mp4,delogo=x=100:y=100:w=150:h=20:show=1"