A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,617
I think some programs do use a sliding window, although AFAIK all of the USA based legacy carriers base their programs on the calendar year.
IIRC A3 did do the sliding window in going from *A Silver (=Blue) to *A Gold (=Gold on Aegean), but now it seems to be twelve months with a mid-late Novemeber closing date for everyone who participated previously.