Admin and Manager users have the ability to customize when and how often their Briefs get sent out by navigating to 'settings' then to 'Briefs'. Two days before the Brief gets sent out, the creator of the Brief (either an Admin or Manager) will get an email reminder previewing the Brief, allowing for changes to be made.
From the time the Brief gets sent out, the Direct Reports have 24 hours to complete the Brief on time. After the first day, the brief will be considered late, but the Reps will still have two more days to complete the brief until it closes. Finally, after a Direct Report submits a Brief, the manager has two days to review it.
You can edit when and how often your Briefs get sent out by navigating to 'Settings' then clicking on the 'Briefs' tab.
Here is an example of the Brief Timing and Calendar of events (Pictures always help)