Count of days in a year used to calculate the amortization.
Convention

Description

Actual/Actual

 Actual count of days in the period
 Assuming there are 365 days in a year and 366 days in a leap year
 Exists in different conventions:

Actual/360

 Actual count of days in the period
 Assuming there are 360 days in a year

Actual/365 Fixed

 Actual count of days in the period
 Assuming there are 365 days in a year

Actual/365L

 Actual count of days in the period
 Assuming there are 365 days in a year and 366 days in a leap year

Actual/366

 Actual count of days in the period
 Assuming there are 366 days in a year

BUS/252

 Usually used in Brazilian contracts and indexes
 Actual count of business days in the period
 Assuming there are 252 business days in the year

30/360

 Assuming there are 30 days in a month
 Assuming there are 360 days in a year
 Exists in different conventions:

30/360 ISDA

 Assuming there are 30 days in a month
 Assuming there are 360 days in a year and 366 days in a leap year

365/360

 Assuming there are 365 days in the period
 Assuming there are 360 days in a year
