Fill a column according to another one's data

Hi all,

Sorry if this is a basic question.

I want to fill a column automatically according to another column data.
I've got column A with the "Date", and column B with "trimester". So if column A has a month between 1-3, in the second column I want T1, if A has 4-6 in B i want T2 and so on.

I hope it makes sense. It has to be something easy and stupid but don't have a clue.

Thanks!!

Hi and welcome
perhaps try ="T"&CEILING(MONTH(A1),3)/3