Quite a few local clock leaks in upstream projects have been identified and reported.
I think, there might be others. This is because I was involved in reporting some of these local clock leaks. They were only fixed, because by chance I happened to read historic Tor trac development discussions, and then using logic to draw the right conclusions, then reported bugs. I didn't read the related source codes nor checked with a traffic analyzer that there are no other local clock leaks. And I find it very likely, that no one else ever did that either, because these issues remained unnoticed for years.
 I remember having read a thread about apt-get. It was mentioned, that it leaks the language to remote servers. Perhaps also installed packages. Among other stuff. Possibly also local clock? Would be good to have a list of these leaks.
1) ask TPO to think through if there are any further local clock leaks -> check Tor for local clock leaks
- 2) research leaks by apt-get 
- 3) figure out, and check using a tshark or wireshark regex that searches for timestamps