↑In Alien, the Nostromo is said to be 10 months from Earth when it sets down on LV-426, in June 2122, meaning it was originally scheduled to return to Earth some time around April 2123. In Aliens, Ripley tells Burke she promised Amanda she would be back for her 11th birthday. It's safe to assume this birthday would have fallen fairly soon after the Nostromo was supposed to return, certainly some time that year, thus if Amanda turned 11 in 2123, she must have been born in 2112.
