Including the start and end dates in the calculation, there are 528 days between the two dates.
There are 231 days in-between March 4, 2011 and October 21, 2011
21 months.
NCIS Los Angeles - 2009 Backstopped 3-3 was released on: Canada: 4 October 2011 USA: 4 October 2011 UK: 9 October 2011 Australia: 11 October 2011 Belgium: 10 November 2011 Netherlands: 13 November 2011 Germany: 1 March 2012 Hungary: 12 March 2012 Japan: 13 July 2012
Between October 24, 2010 and March 1, 2011 there are 128 days.
Glee - 2009 Duets 2-4 was released on: Canada: 12 October 2010 USA: 12 October 2010 Netherlands: 15 February 2011 Spain: 2 March 2011 Japan: 27 March 2011 Belgium: 30 April 2011 Germany: 12 September 2011 Finland: 19 September 2011
NCIS Los Angeles - 2009 Deadline 3-4 was released on: Canada: 11 October 2011 USA: 11 October 2011 Australia: 18 October 2011 Belgium: 17 November 2011 Netherlands: 20 November 2011 Germany: 8 March 2012 Hungary: 19 March 2012 Japan: 20 July 2012
NCIS Los Angeles - 2009 Harm's Way 2-18 was released on: Canada: 1 March 2011 USA: 1 March 2011 Netherlands: 9 May 2011 Belgium: 8 September 2011 Japan: 6 October 2011 Germany: 27 October 2011 Hungary: 14 November 2011
Glee - 2009 The Substitute 2-7 was released on: USA: 16 November 2010 Spain: 23 March 2011 Japan: 17 April 2011 Germany: 3 October 2011 Finland: 10 October 2011
Glee - 2009 Furt 2-8 was released on: USA: 23 November 2010 Spain: 30 March 2011 Japan: 24 April 2011 Germany: 10 October 2011 Finland: 17 October 2011
United States of Tara - 2009 Abundance 1-8 was released on: USA: 8 March 2009 Spain: 8 June 2009 Hungary: 18 August 2009 Australia: 16 September 2009 Germany: 25 March 2011 Japan: 20 August 2011 Finland: 17 October 2011
United States of Tara - 2009 Alterations 1-7 was released on: USA: 1 March 2009 Spain: 1 June 2009 Hungary: 18 August 2009 Australia: 9 September 2009 Germany: 25 March 2011 Japan: 13 August 2011 Finland: 10 October 2011
Parks and Recreation - 2009 Camping 3-8 was released on: USA: 24 March 2011 Hungary: 21 October 2011