Skip to content

Day Count Conventions

A Day Count Convention determines how interest accrues over time for a variety of financial instruments, such as bonds, loans, and mortgages. It defines two things: 1. How to calculate the number of days between two dates. 2. How to calculate the number of days in a year.

LibreFolio supports the following conventions:

ACT/365 (Actual/365)

  • Days: The actual number of days between two dates.
  • Year: Assumed to be 365 days.
  • Usage: Common in UK money markets and for some government bonds.

ACT/360 (Actual/360)

  • Days: The actual number of days between two dates.
  • Year: Assumed to be 360 days.
  • Usage: Very common in US money markets and for commercial loans.

30/360 (Bond Basis)

  • Days: Calculated assuming every month has 30 days.
  • Year: Assumed to be 360 days.
  • Usage: Standard for US corporate bonds and many municipal bonds.

ACT/ACT (Actual/Actual)

  • Days: The actual number of days between two dates.
  • Year: The actual number of days in the year (365 or 366 for leap years).
  • Usage: Standard for US Treasury bonds.