The 20th of October.
120 days after Monday, Feb 22, 2010 = Tuesday, June 22, 2010.
The 11th of October is 120 days before it. In a normal year, the 8th of June is 120 days after it. In a leap year, the 7th of June is 120 days after it.
June 21, 2010 + 120 days = October 19, 2010.
Adding 120 days to June 1 gives September 29.
1st February falls 120 days before June 1st.
Adding 120 days to June 9, 2010 gives October 7, 2010.
Adding 120 days to June 15 in any year gives October 13.
Adding 120 days to June 13, 2011 gives December 10, 2011.
Adding 120 days to June 13, 2010 gives October 11, 2010.
In a non-leap year, the day 120 days before June 17 is February 17. In a leap year, such as 2008, the day 120 days before June 17 is February 18.
120 days after Thursday, April 22, 2010 = Friday, August 20, 2010.
Adding 120 days to October 22, 2010 gives February 19, 2011.