since 2011 ends in a 1 and 1981 ends in a one all you have to do is count the tens
1981-1991=10 yrs.
1981-2001= 20 yrs.
1981-2011=30 yrs.
its really obvious
If you are born on 1981-2011 you are 30 years old
Entertainment Tonight - 1981 2011-01-04 was released on: USA: 4 January 2011
Entertainment Tonight - 1981 2011-01-05 was released on: USA: 5 January 2011
Entertainment Tonight - 1981 2011-01-06 was released on: USA: 6 January 2011
Entertainment Tonight - 1981 2011-01-07 was released on: USA: 7 January 2011
Entertainment Tonight - 1981 2011-01-11 was released on: USA: 11 January 2011
Entertainment Tonight - 1981 2011-01-12 was released on: USA: 12 January 2011
Entertainment Tonight - 1981 2011-01-13 was released on: USA: 13 January 2011
Entertainment Tonight - 1981 2011-01-18 was released on: USA: 18 January 2011
Entertainment Tonight - 1981 2011-01-19 was released on: USA: 19 January 2011
Entertainment Tonight - 1981 2011-01-20 was released on: USA: 20 January 2011
Entertainment Tonight - 1981 2011-01-21 was released on: USA: 21 January 2011