on/at the stroke of eight, midnight, etc.
on the stroke of (some specific time)
Exactly at a specific time, especially the very beginning of the hour. 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!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
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.
Farlex Partner Idioms Dictionary © Farlex 2017