One year, my two daughters and I went to the mall and Linens and Things on Christmas Eve. All of the day-after-Christmas items were already marked down and the malls were practically empty.
It may have been a fluke, but it dawned on me, that unless these stores have elves that come in, in the middle of the night, this stuff has to get marked down/advertised as being marked down, before the stores re-open on the 26th. If they're advertising it, they have to offer it, right?
I have never put this to the test, but for anyone who lives in Houston and has a Foley's, they have what are called Red Apple sales, and they always started marking items down the night before. If you were lucky enough to be there, then you got the savings, minus the crowds.
Disclaimer :If some of you trek to the mall on Christmas Eve, and find that I'm wronger than wrong, then this was actually my husband that typed this and not me. If you get wonderful discounts... it was me. Believe at your own risk.