Twins born in different years

A set of twin boys were delivered ten minutes apart.  One in 2016 and the younger one in 2017.  New Years Eve is the only day when this can happen.  The boys were born in Glendale, AZ and their father joked that the older one would tease the younger one about being born in different years.  A set of girls was born four minutes apart in San Diego, CA and will also have different years on their birth certificates.  twins a year apart