Which ring will let me try out the B dashboard?

Are you in the Dashboard Preview program? Which ring?

I'm in Alpha ring and we didn't get an update this week, last one was Dec 19, 2018 IIRC.

Have you tried clearing out your system cache yet?

Clearing System Cache:

From the xbox dashboard, Go to Settings>System>storage>Press Y to select a storage device (Does not matter which one)>Clear system cache>Yes

Try and see if this solved the issue.

Let us Know!

Hey there Equ1nox,

Sorry to hear you're not getting your dashboard updated.

• We just rolled out a new dashboard today which should help resolve this for you.
  

If you're still seeing the same old adds, I would try
downloading your profile.

Please let us know how things go and we'll work from there.

Im not sure if that's the specific dashboard update everyone is on now, i just checked my time played for DayZ and it's pretty accurate and still counting up.

But I'm also on the insider program which puts me on a different dashboard. Certain insider rings are having time tracking issues though.

I believe this was fixed for people in the alpha ring of the Xbox insider program on March 8th: -

"We have resolved the issue in which your Wi-Fi connection would lag for 3-4 seconds and reoccur after 30 minutes"

This fix has already filtered down from the alpha ring to a couple of the lower preview rings, and it should be included in the public build of the dashboard which I would imagine will be pushed out in early April, although that's just an educated guess.
It might be a little sooner, it might be a little later.