Event.timeStamp reveals startup time
Experimenting with JS Events, I noticed the following:
If I open a web page's console in standard Firefox and enter
it returns a number like
This corresponds to the number of microseconds since the epoch. I confimed this result by entering:
window.setInterval(() => console.log(new Event("asdf").timeStamp), 1000)
and it prints out
1442000426991504 1442000427990600 1442000428989561 1442000429989980 1442000430990465 1442000431990790 1442000432989823 1442000433989783 ...
This violates the web standard, which specifies milliseconds since the epoch: http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113/events.html#Events-Event-timeStamp
Tor Browser gives similar result, but rounded to the nearest 100 microseconds, because of TBB's #1517 (moved) patch.
In any case, that's not the usual way to use Events. A more typical usage is:
window.addEventListener("mousedown", e => console.log(e.timeStamp))
If I click the mouse once per second (by listening to a clock) I get:
1028609 1029641 1030609 1031641 1032617 1033609 1034601 1035601 ...
which indicates that the results are expressed in milliseconds. The epoch, however, is defined differently. In this case it reveals the system startup time, which is a linkability issue.