The months all use the definite article, so we need to use 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
We can now ask and answer these simple questions.
Cuin a rugadh tu?
When were you born?
Rugadh mi anns a’ Mhàrt
I was born in March
Rugadh mi anns an t-Samhain
I was born in November
Cuin a tha co-là-breith aig Sìne?
When is Jane’s birthday?
Tha e anns a’ Ghiblean
It’s in April