I am assuming that the attention a question gets depends to some extent on when it is submitted. If this is the case, would it not be sensible to ask the question when it is most likely to be noticed? My guess is that this would be the weekend.
There aren't so many quesitons being asked here that you risk going unnoticed unless you post on the optimal time. Just post whenever you want to. The timing is really a non issue.
If you are concerned about not getting good answers, I would suggest you read "How do I ask a good question?". That will be more useful than trying to get the timing right.