All months take the definite article and follow the normal rules for the dative case.
anns an Fhaoilleach
in January
anns a’ Ghearran
in February
anns a’ Mhàrt
in March
anns a’ Ghiblean
in April
anns a’ Chèitean
in May
anns an Ògmhios
in June
anns an Iuchar
in July
anns an Lùnastal
in August
anns an t-Sultain
in September
anns an Dàmhair
In October
anns an t-Samhain
in November
anns an Dùbhlachd
in December
Play with the answers until you are happy with
Dè bhios tu a’ dèanamh?