Which preposition to use with lupercalia

as Occurrences 1%

[-30-] "Even this result did not sober him, but when he was consul he came naked, naked, Conscript Fathers, and anointed into the Forum, taking the Lupercalia as an excuse, then proceeded in company with his lictors to the rostra, and there harangued us from the elevation.

in Occurrences 1%

Of the famous Lupercalia in February, and some other festivals which neither died out altogether nor were converted into ludi, we only know the ritual, and cannot tell whether they were still used as popular holidays.

Which preposition to use with  lupercalia