The selected Leap Year convention determines the number of days assumed in a leap year. The conventions supplied by Resolution are defined as follows: 



Convention 
Definition 
. 

Actual 
The number of days in a leap year is 366. The number of days in a nonleap year is 365. 
365 
The number of days in every year is assumed to be 365, even in a leap year. 
365 ISDA 
The number of days in a leap year is 366, and the number of days in a nonleap year is 365. However the DayCount fraction (the proportion of a year) is calculated using the following formula: Result = Days_{ly} /366 + Days_{ny} / 365 Days_{ly} = Actual number of days in period that fall in a leap year. This contrasts the Actual/365 DayCount fraction which is determined by dividing the actual number of days in the period (regardless if there is a leap year) by 365. 
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