ACT ACT(AFB)Subtype of
The AFB convention, also known as Actual/Actual Euro
Let [T₁,T₂) be the period between two dates T₁ and T₂, of which the length L in annual units must be calculated
Let N be the number of days of [T₁,T₂), with T₁ included and T₂ excluded.
Let N' be some specially defined nominal number of days of [T₁,T₂), calculated as follows:
If the period [T₁,T₂) does not exceed one year, N' equals either 366 or 365 depending on whether the leap day 29 Feb is in [T₁,T₂) respectively, whereby the last date T₂ is not considered.
If the period [T₁,T₂) exceeds one year, the calculation is split into two parts:
1) The number of complete years, counted back from T₂
2) The remaining initial stub, calculated using the basic rule.
L = N/(N')