## ACT ACT

Subtype of NameThe ISDA convention, also known as

**,**

*Actual/Actual (Historical)***,**

*Actual/Actual***, and according to ISDA also**

*Actual/Actual ISDA***,**

*Actual/365***, and**

*Act/365*

*A/365*Let

**be the period between two dates**

*[T₁,T₂)***and**

*T₁***, of which the length**

*T₂***in annual units must be calculated**

*L*Calculation rule:

Let

**be the actual number of days of the period**

*N₁***that happen to fall in a leap year**

*[T₁,T₂)*Let

**be the actual number of days of the period**

*N₂***that happen to fall in a normal year**

*[T₁,T₂)*Then

*L = N1/366 + N2/365*