According to
http://www.thepeerage.com/index.htm
Anne was born circa 1501and Mary in 1506 .
Anne, Marchioness of Pembroke b. c 1501, d. 19 May 1536
Mary b. b 1506, d. 19 Jul 1543....but in the separate bios it says Mary was born before 1506 ..
Another source says .........
Information about the life of Mary Boleyn is sketchy at best. Before her sister's ascendancy, Mary was the most famous member of her family, a dubious honor since it was based upon her adulterous affair with King Henry VIII. There has been great debate over the exact year of her birth, with many researchers unable to agree on which Boleyn sister was older. Some speculate Anne was born in 1501 or 1502; others place it at 1507. The most recent scholarship supports 1507 as the year of Anne's birth. Mary was born a year later, in 1508.
http://englishhistory.net/tudor/citizens/boley n.html