If on 15 March 2012 the day was Monday , then what was the day on 15 March 2016 ?

Saturday

In case of leap year we have to add 2 odd days (applicable in case of january and february ) and in any other case we have to add 1 odd day.

 15 March 2012 - Monday

 15 March 2013 - Wednesday 

 15 March 2014 - Thursday

 15 March 2015 - Friday

 15 March 2016 -  Saturday