Google panda update list till now
Panda 3.9 on July 24th
Panda 3.8 on June 25th
Panda 3.7 on June 9th
Panda 3.6 on April 27th
Panda 3.5 on April 19th
Panda 3.4 on March 23rd
Panda 3.3 on about February 26th
Panda 3.2 on about January 15th
Panda 3.1 on November 18th
Panda 2.5.3 on October 19/20th
Panda 2.5.2 on October 13th
Panda 2.5.1 on October 9th
Panda 2.5 on September 28th
Panda 2.4 in August
Panda 2.3 on around July 22nd.
Panda 2.2 on June 18th or so.
Panda 2.1 on May 9th or so.
Panda 2.0 on April 11th or so.
Panda 1.0 on February 24th