Originally Posted by
MSPeconomist
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.
Actually Jet Airways has sort of a sliding window, looking back 6, 12 and 24 months with diff. criterias. But wont help OP if flying SK ;-)