Schedules with opening hours, a closed message, and somewhere to send callers after hours.
Tell the system when you are open, and what should happen when you are not.
A schedule
A schedule has opening hours for each day of the week, a time zone, and two destinations: where calls go when open, and where they go when closed. There is an optional message to play to someone who calls after hours.
Closed calls can go to a mailbox, the on-call group, a menu, or an outside number such as an answering service.
Apply it to things
Most offices do not want to think in schedules. They want "the front desk is closed after five." So a schedule can be applied to an extension, a ring group or a menu, all from one page. Whenever an outside call is on its way to that thing and the schedule says closed, the caller hears the message and goes where the schedule sends them.
Calls between desks are never turned away. If you are in the office at seven in the evening and dial a colleague, their phone rings.
The override
A schedule can be forced open or closed by hand until someone puts it back to automatic. That covers the staff meeting, the power cut, the early close before a holiday, or the first good swell of the season.
Outside numbers, safely
Sending callers to an outside number is the one place the system dials out on its own. The number is typed by an administrator and checked against the dialing rules when saved. A caller can never choose it. That is what keeps after-hours forwarding from becoming a way for strangers to make calls on your account.
One per thing
Each extension, group or menu can have one schedule. Different departments can keep different hours.