Do Not Disturb, as to activation, seems to not be capable of quite what you ask, not on a Vodavi Starplus STS system.
One: the Vodavi system can be programmed to give each phone station a DND button.
Then, the Do Not Disturb function must be activated by pressing that button on the station.
(If no DND button is programmed, you simply activate DND for the phone station by dialing
and then dial 631 again later, to turn ringing back on again and disable DND mode for that phone station.)
Perhaps some other mode would be your preference, if you just want the ringers on all the phones to stop for the night and start up again automatically in the morning. ?
(If this answers your question, please rate my answer. Thanks.)