As a user of the annotation module, I can see last modification dates of comments and sticky notes and post-its in a relative format:
“3 minutes ago”
“14 hours ago” …
If I hover the date displayed like this, I can read the exact time, formatted with the locale of the browser.
Note : a typical library to do this is “moment.js”
There should be no inconsistency in the display according to the dates of the browsers and the HMI server.