question Best time (GMT) to end an Auction

You might find these 2 articles helpful:

https://namebio.com/blog/the-best-day-for-your-domain-name-auction-to-close-on/

https://support.flippa.com/hc/en-us/articles/207303197-What-is-the-best-time-to-end-my-auction-

Both the above links are very useful.

I've not used GoDaddy for 7-day auctions, so I don't know if they have a system in place which allows sellers to commence their auctions at a pre-determined day/time.

With GoDaddy, it can take up to 72 hours for a domain to be approved, so it can all be a bit hit and miss.

Flippa's approval process seems faster (normally) and allows for more precise start timings.