You can find them in the Admin CP under the "Tools" tab. XenForo has its own built-in cron system and doesn't use the system cron. They don't run at a particular time though, since a request has to be made for them to be triggered. So it's essentially run on the first request after a certain time.
The reason I was looking is I am trying to find the cause of a problem we are having with Xenforo. This is a sample of the reports of the problem, which have been made by a few dozen of our site members.
Twice now while I've been just reading a page, I've had 100% CPU spikes in the browser (enough to basically freeze the computer for 10-20 seconds).
I was looking for something on the server side to be causing this, which is why I was tracking down cron activity. The CPU surge is causing me to suspect this problem occurs in connection with ajax scripts running in the background. All the reports say the problem occurred while a Xenforo page was the active page in their browser. It's been reported on Chrome and FireFox.
Any suggestions on how we can figure out what is happening and fix it?
It's very unlikely to be cron. It's possible but unlikely. You'd need to look at your raw web server logs to see if you see a large number of requests to deferred.php at the exact time they're reporting the problem.
Unfortunately I can't see the thread in question, but it could be something relating to the content of the thread or elements of your style (or ads).