How is "simultaneity" in transactions achieved, and when is it necessary?

Question

I can think of two ways. One is to have everyone connected, either physically (in the same room) or electronically, via e.g. Zoom, to execute their documents. A second way might be to have different people execute their documents on different days, and put them in escrow. When the last required deliverable has been received, there is an opening or "break" of the escrow.

Are these valid ways to achieve simultaneity, and are there "third" ways that I have missed?

When is this necessary, or at least advisable? Are these procedures mainly for contracts, or are there other uses for them?

Answer 1

Both of those are indeed common. In some legal contexts, it is agreed by convention or by specific agreement that two events will be treated as simultaneous if they occur within a defined time interval. For example, in inheritance law it is often agreed that two people will be considered to have died at the same time, so that neither inherits from the other, if they die within 30 days of each other. (Before this was a common agreement inheritance sometimes depended on establishing which of two people died first, perhaps only by a matter on minutes, which was not always easy to do. See Sayers's The Unpleasantness at the Bellona Club for a fictional case depending on such an issue.)