Earliest time a Build has been released is 10am Redmond time, but Builds have been released as late as 6pm Redmond time.
Terry Myerson is head of Windows Division Terry Myerson sent down an order banning the use of the word "RTM" amonst all Microsoft employees.
It's Redmond Washington 10AM when they normally release updates or new builds. 19:00 aka 7PM amsterdam time, would be 18:00 aka 6PM in England. Normally Dona tweets at 8AM Redmond time if there won't be a new build that day.
At least later, yes. If there is a convention or visit abroad it can be a late release. But standard it's 10AM Redmond time.