When I create a new Change Order, I can set the field "need_by_date".
Is there any functionality on this field? Any event that is fired or notification that is sent, when the time has arrived?
No. There is no event that will be fired. An event will always be fired, when the delay time, defined in the event detail, is expired.
The "need_by_date" field is just an attribute of a Change Order.
But you may use this in a Stored Query and attach this to the analyst's Scoreboard. There is already one predefined Stored Query with the label
"Scheduled for this week". This will show all Change Orders, where the need_by_date will expire within this week.