Just booked @ 19:30 PT, and it's also saying Sept 28 in the email and Sept 27th on the app manage booking page.
It better work, as I've changed destination and spent an extra $400 to qualify for 35K.
They've just put out another 10/20% off code as well: RRDPPHA1
All sorts of fine print, but if you're leaving it late it might save you a few dollars depending on your routing/fare.