It would be September 13 2011!
90 days after Tuesday, December 28, 2010 = Monday, March 28, 2011.
There are 59 days between December 28 2010 to February 24 2011!
There are 177 days between December 28 2010 and June 22 2011.
13 days until the 11th of December 2010 (from 11/28/2010).
Adding 180 days to December 30, 2010, gives June 28, 2011.
Adding 210 days to May 28, 2010 gives December 24, 2010.
There are 392 days from 28 November 2009 until Christmas Day 25 December 2010.
From December 28, 2009 until March 21, 2010 there are 83 days inclusive.
28 weeks and 5 days.
December 28 2010 was a Tuesday.
Including the start and end dates in the calculation, there are 365 days between the two dates.
It's not clear whether you want those two dates included in the count. Tell you what ! Here's a list of all the days in that neighborhood. You should be able to count the ones you're interested in. December 28, 2009 December 29, 2009 December 30, 2009 December 31, 2009 January 1, 2010 January 2, 2010