Adding 285 days to December 15, 2010 gives September 26, 2011.
731 days after it is Saturday the 15th of December 2012. 731 days before it is Sunday the 14th of December 2008.
The date 350 days from 15 December 2010 is Wednesday, November 30, 2011.
The date which falls 90 days after December 4, 2010 is March 4, 2011.
The term "15th prox plus 30 days" refers to a payment or deadline that is due on the 15th of the next month (prox) plus an additional 30 days. This means that if today is, for example, October 1st, the due date would be November 15th, and adding 30 days would extend the deadline to December 15th. Therefore, the final due date would be December 15th.
185 days but that may be wrong because I'm only 11, though I'm very good with maths
Subtracting 251 days from December 15, 2009, gives April 8, 2009.
Adding 333 days to June 15, 2010 gives May 14, 2011.
Sunday, September 26 2010 is 90 days before December 25 2010.
Subtracting 126 days from December 10, 2010 gives August 6, 2010.
Adding 120 days to December 24, 2010 gives April 23, 2011.
Adding 120 days to December 6, 2010 gives April 5, 2011.
330 days after January 7, 2010 is December 3, 2010.