Asuka Langley Soryu
Adult characters' birth years were simply calculated from their age, but there was an additional aspect in determining the children's ones. According to the Japanese educational system, in 2015 second graders of junior high school (eighth graders) are basically made up of children who were born from April 2, 2001 to April 1, 2002. Children's birth years were set in proportion to this rule. However these birth years did not change the children's ages of 14 in year 2015. This is the reason why Asuka Langley Soryu and Toji Suzuhara were born in December 2001 and Hikari Horaki was born in February 2002, despite all children except Kaworu are 14 in 2015.