The netlog uses a timeTickOffset to convert TimeTicks values to Dates for display. I imagine most TimeTicks use this kind of approach.

Should we expose a function that performs the same job as UnixEpoch, but just provides TimeTicks::Now() as the reference time?

TimeTicks ApproximateUnixEpoch() {
  return TimeTicks::Now() - (Time::Now() - Time::UnixEpoch());
}

Or, should we instead provide a function like:

TimeDelta ApproximateTimeSinceEpoch(TimeTicks t) {
  return (Time::Now() - Time::UnixEpoch()) - (TimeTicks::Now() - t);
}

WDYT? Netlog would probably like option (1), but option (2) is a better interface. Who wants Epoch time in TimeTicks format? Seems like a bad idea. We could also expose an interface from TimeTicks => Time.

Could you give some context on why Netlog wants to find the time since the Unix epoch in TimeTicks? It seems that the main problem is that this question is just inherently unanswerable. I guess my problem with "approximate" is that it's vague as to just how far off the answer really is.

I'm going to tentatively say "nevermind," as I'm looking through the code. It feels like the best thing to do is to just log a reference Time and TimeTicks at netlog creation time, and perform all Time conversions using the initial Time reference plus a TimeDelta calculated via TimeTicks.

Another question:
https://code.google.com/p/chromium/codesearch#chromium/src/net/base/network_quality_estimator_unittest.cc&l=360

This test uses UnixEpoch to mock a "very old" timestamp. What's the canonical way to do this? I imagine there's something better than using FromInternalValue.

Now - a large delta? Using Now is usually pretty sketchy in a test though.. maybe ok in this case?

Now - a large delta produces a TimeDelta. We'd have to coerce that somehow into a TimeTicks to satisfy the existing API.

Oh, woops. Well, FromInternalValue isn't terrible in a test either, is it causing some problem?

https://code.google.com/p/chromium/codesearch#chromium/src/base/time/time.h&l=329

Are you sure it produces a delta? Which operator are you meaning?

Sorry I was unclear about the API, Now() - TimeDelta can give a TimeTicks. Fixing all cases in net/ will happen soon.

You started fixing this bug over two years ago. Are you still working on it? 

Yes.