<Tr> <Th> Alberta </Th> <Td> AB </Td> <Td> Alta . </Td> <Td> Alb . </Td> <Td> </Td> </Tr> <Tr> <Th> British Columbia </Th> <Td> BC </Td> <Td> B.C. </Td> <Td> C. - B . </Td> <Td> C. - B. is short for Colombie - Britannique </Td> </Tr> <Tr> <Th> Manitoba </Th> <Td> MB </Td> <Td> Man . </Td> <Td> Man . </Td> <Td> </Td> </Tr> <Tr> <Th> New Brunswick </Th> <Td> NB </Td> <Td> N.B. </Td> <Td> N. - B . </Td> <Td> N. - B. is short for Nouveau - Brunswick . </Td> </Tr>

When did the state abbreviations change to 2 letters