The 143rd day in 2010 is the 23 May. 31 days in January 28 days in February 31 days in March 30 days in April 120 leaving 23 days needed in May.
100 days before the 1st of May is the 21st of January in a normal year and the 22nd of January in a leap year. 100 days after the 1st of May is the 9th of August.
334 days after Thursday, May 20, 2010 = Tueday, April 19, 2011.
100 days before Monday, May 3rd, 2010 = Saturday, January 23, 2010.
The answer depends on the starting date, as some months have more days than others. 523 days after Friday, May 21, 2010 = Wednesday, October 26, 2011. The answer, in this case is a Wednesday.
120 days from May 5 2010 is Thursday, September 2, 2010.
Adding 120 days to May 20, 2010 gives September 17, 2010.
Adding 120 days to May 11, 2010 gives September 8, 2010.
January 17 + 120 days = May 17 (except in a leap year).
Adding 120 days to January 28, 2011 gives May 28, 2011.
Subtracting 120 days from September 13, 2010 gives May 16, 2010.
Adding 120 days to January 9, 2012 gives May 8, 2012.
Adding 120 days to January 27, 2011 gives May 27, 2011.
120 days after Mon, May 31, 2010 = Tue, Sep 28, 2010.
Adding 120 days to January 7 in a non-leap year gives May 7 of the same year. Adding 120 days to January 7 in a leap year gives May 6 of the same year.
I think the date will be January 22, 2010 120 days before may 23.
Adding 120 days to May 29, 2010 gives September 26, 2010.