Shameless plug: https://petertodd.org/2016/opentimestamps-announcement https://petertodd.org/2016/opentimestamps-announcement and for Git commits https://petert

Shameless plug: https://petertodd.org/2016/opentimestamps-announcement https://petertodd.org/2016/opentimestamps-announcement and for Git commits https://petertodd.org/2016/opentimestamps-git-integration https://petertodd.org/2016/opentimestamps-git-integration Bitcoin timestamping can be a lot more convenient and efficient than that site, and totally free too.