The Activation Scheduler
This feature is part of the BetterFumbblExperience extension. For details on it check here.
The Activation Scheduler is easily the most complex feature in BetterFumbblExperience and comes with a bunch of features on its own:

The Activation Scheduler looks much like the Activation Window but is in fact something different. It allows you to 'schedule' a Team Activation. The Activation Scheduler will open the Activation Window 4 minutes prior to the next draw and execute a Team Activation automatically. If you pay attention you will see the Team Activation screen appear for a second and then after successful request disappear again. This is merely a design choice to visualize to the user what is happening. It isn't actually necessary for it to pop up.

If you use the Activation Scheduler during Activation time, it will activate/deactivate immediately just as if you had clicked the Activate/Deactivate buttons in the other window. This procedure is recommended because you'll miss out on the new status window otherwise.



The Status Window
The status window has four states.

Deactivated (Default State)
When you open the Scheduler it will usually be deactivated, regardless of whether you are or aren't in Activation time.

Timer
When you click Schedule! and aren't more than a minute into activation time a timer will start running to show you how close it is to schedule the next activation.
This is a quite important moment because the moment the activation happens, you will be scheduled even if you close the Blackbox Window.
While the Timer is still running you could as well just leave the Blackbox page. The activation won't be executed since the Activation Scheduler works only while Blackbox page is open.
For good procedure it is still recommended that you stop the timer before you leave. Just so you don't mess with these things. It is reliable but also your risk, so be cautious. Better to just treat it like a regular activation.

Activating...
Activating means the Activation is about to happen.

Activated
'Activated' state is the point of no return so to speak. The server has been informed. You could shut your computer off, you might still get a game unless you click Deactivate/Unschedule.
Your state will be displayed correctly regardless whether you have closed your window in the meantime or not used the scheduler at all. It is a cookie based feature so the only way to make it dysfunctional would be to disregard the cookie. (Not accepting cookies on Fumbbl would cause you much fatal problems anyways.)


Why is it build this way?
For one, because I don't have access to the server. .For another because I don't want to mess with the server. So all the tools are aimed to add to the Fumbbl functionality without actually replacing anything. Most things the server would normally do are handled here by cookies. But obviously cookies are dependent on your own browsing behavior and don't work when your browser is shut off for instance.

How does the clock work?
The clock was an interesting compromise between fetching server time and using the local computers clock to keep pressure to the server to a minimum. Essentially all the tools aim to not stress server ressources and box already does a lot of time requests on default.
So what is happening here is that the server time is fetched when you open blackbox and is compared to your local clock. If your local clock is out of sync, the scheduler clock will use a readjusted local timer that is counting numbers based on server time rather than your clock time.
If however your clock isn't able to count seconds correctly, the clock would still run out of sync with the server. However, that's rather unlikely. In any case, since scheduling and activations happen 4 minutes prior to the draw, that shouldn't be much of an issue.

Otherwise it should completely not matter if your clock is 23 mins and 14 secs off or whatever. The tool is perfectly able to handle it.