Originally Posted by
COpltASgldPHX
Since SDC is only offered online during OLCI, and OLCI is only available @ 23:59 prior to departure, it would be impossible to SDC to the same flight one day earlier.
On my last itinerary, I changed my return flight CO1521 ATL-IAH from Friday to the same flight on Thursday. I did this through co.com using the "Change Flight" link about 27 hours before my original departure. All co.com wanted was my $25 (plat) SDC fee.
The website did error out when it tried to take my payment, but it did change the flight in my reservation. At that point, I just called the elite desk to take my payment.
I dunno, maybe it was a website glitch and I got lucky that day.