When you are creating a survey, you can choose how often it would be asked and on what day of the week.
It will be triggered on that day you selected at 9am UTC.
So if you choose the review to run every three months on Mondays - it will trigger first time next Monday at 9am, UTC. And than repeat on Mon, 12 weeks later.
You'll be able to see the exact date it will be sent on the review page: