I can never remember myself. I’ve moved your topic to the ToS category. Hopefully someone in the know will weigh in on the question.
Edit: my guess though is as long as you started your ride during the open window then it will “count” even if you finish it after it closes. I don’t believe you can start before it officially opens then finish and save after it has opened.
This question gets asked a lot, see this: Official Tour of Sufferlandria 2022 Route Discussion Thread - #293 by Glen.Coutts
Edit 2: now my guess is you have to complete it within the open window so maybe you can start it before it opens. WTH do I know. My advice, wait for an official answer or ask a minion. 