The Associated Press writes:
According to ISU rules, skaters must be 15 by the preceding July 1 to compete at an Olympics or senior world championships, and 14 for other senior-level international competitions, such as the Grand Prix final. Junior skaters must be at least 13 the previous July 1 but cannot have turned 19 (singles) or 21 (pairs and ice dancers).
According to the records found by the AP on the federation website, Zhang Dan was born Oct. 4, 1987, meaning she would have been only 14 when she and Zhang Hao - no relation - competed at the 2002 Olympics and world championships. The Zhangs were 11th in Salt Lake City and ninth at worlds.
Zhang Hao, meanwhile, was born on Feb. 6, 1982, according to his birthdate on the federation website. That would have made him too old to compete at the 2003 junior world championships, which they won.