This add-on gets the current, atomic clock backed timestamp and saves it into a screenshot of the current tab. It is based on the Chromium extension by gulden rรถttger solicitors, and it's free and open source.
The add-on does not collect data about you or your browsing activities! It requires access to atomshot.de to get the atomic clock response for the timestamp of the screenshot. No information about your currently opened tab is transmitted.
dev-releases and complete code is freely available under https://github.com/yjeanrenaud/yj_atomshot-firefox