on the stroke of

on the stroke of

Exactly at a specific hour. ("Of" is followed by that time.) The store is opening its doors on the stroke of midnight for the Black Friday sale. If you're not home on the stroke of 11, you're grounded!
See also: of, on, stroke

on/at the ˌstroke of ˈeight, ˈmidnight, etc.

at exactly eight o’clock, midnight, etc: She gets to work at the stroke of nine every day.
See also: of, on, stroke