# Day count convention confusion

For example I want to calculate a year fraction between the dates: 2011.03.31 and 2015.05.30.

There are 1521 days between the two dates, but 2012 was a leap year. So what should I use in the denominator? 366 or 365 if I want to use the ACT/ACT convention?

• Number of days in 2012. – HelloWorld Aug 4 '16 at 15:52

• My way of doing it is like this (same answer of course), year by year: $275/365+366/366+365/365+365/365+150/365$ = 4.16438 – Alex C Aug 5 '16 at 0:27