The day that is 180 days after 31 December 2011 (the 180th day of 2012) is 28 June 2012.
The date which falls 90 days after December 4, 2010 is March 4, 2011.
Adding 180 days to July 1, 2011 gives December 28, 2011.
Adding 120 days to June 13, 2011 gives December 10, 2011.
Adding 179 days to December 20, 2010 gives June 17, 2011.
Adding 120 days to December 13, 2010 gives April 12, 2011.
Adding 240 days to December 23, 2010 gives August 20, 2011.
Adding 120 days to December 23, 2010 gives April 22, 2011.
Adding 120 days to December 3, 2010 gives April 2, 2011.
Adding 120 days to December 14, 2010 gives April 13, 2011.
The date which falls 90 days after February 2, 2011 is May 3, 2011.
Counting from December 1, 2011, adding 90 days to this date gives February 29, 2012.
The 10th of December.