I think a minimum of 2 days later.
Suppose you placed an order to sell on Monday December 24th before the market closed and the order was accepted. Then you would see the shares were sold by looking at your account on Christmas morning December 25th, but the actual money would be no where. Then overnight on December 26, Vanguard would do an ACH transfer to your checking account. If your checking account was any good, then it would be there on the morning of December 27th if you looked.
It's all about short-term opportunistic rebalancing due to a short-term change in one's asset allocation, uh, I mean opportunistic rebalancing, uh I mean rebalancing, uh I mean market timing.