Overwhelmingly my best day for everything is Saturday. Sold two out of three domains on a Saturday. Most parking clicks Saturday. Most for sale lander uniques also Saturday. Most ad clicks Saturday as well.
Often there are multiple people going for a domain at the same time. Either the final user OR someone who got informed about the deal and wants to squeeze in as the middleman. Or sometimes the competition of that business. One of them might not know yet that the domain has sold already.
I don't think you can accurately pin point the best day, regarding a lead. Maybe you'll get more people in the thread saying Tuesday more than Saturday, or Friday more than Monday, but I'm not sure if that's an accurate justification, as each situation in the moment, is unique in itself. The "best time" for enquiries in a day could be the evenings, when people have finished work. Alternatively, for others its during the day at work, as this is the time for business, maybe even lunchtime...
Finalising the sale. I don't believe buyers are necessarily putting the money in on a Tuesday, any more so than a Thursday. Maybe the mind-set of some is to do it ASAP, maybe the mind-set of others is to deal with it at the weekend, if they have confidence from the seller that he / she is willing to wait until then. Maybe the domain is expensive and it needs to be thought over, the judgement day of that is then up to the other side....that could be any day. Its going to be different each time. Too many variables, IMO