Your team is in Paris. Who owns the US publishing clock?

Use an explicit timezone and a full date in the production brief. Store an unambiguous timestamp in the workflow and show the intended local time wherever a human approves the schedule. Daylight-saving changes deserve a check when a recurring plan spans them.

Assign one owner to schedule changes and preserve a record of the approved version. The useful guarantee is that everyone agreed on the same instant. A particular posting hour is still a hypothesis to test against the audience you actually reach.