Back in time with Vim

My college came by my desk today wanting to know how to go back in time with vim. He had been undoing and redoing a lot and suddenly realised he had messed up his buffers. I had never heard about going back in time with vim, but Google had the answer on this post: lifehacker.com/202093/go-back-in-text-file-time-with-vim-70.

Apparently the past is but a :earlier 10m away!