I took a small bite last Friday after 6 straight days of market decline. .
It is not a shortened trading day, so you can react to news all the way up to 4 pm Eastern.I suppose anything can happen tomorrow because it will be a thinly traded and shortened trading day, but apparently the late word tonight is the fiscal cliff resolution talk is again stuck at another impasse in the senate.
I got a note from my brokerage that said the market closes at 2 pm. I looked again, it is the bond market. You are right, the stock market goes to 4 pm.It is not a shortened trading day, so you can react to news all the way up to 4 pm Eastern.