をもって

をもって marks the point in time, method, or basis from which something starts, ends, or changes. It has a formal tone and is often used in official announcements, contracts, meetings, and proclamations. It is not about the means of doing something in general; rather, it designates the moment or basis that triggers a new state, rule, or conclusion. Common usages include indicating when something takes effect, ends, or when an action is performed as of a certain date or with a certain criterion.