The Day Count Convention is a standardized methodology for calculating the number of days between two dates.
Most money market deposits and floating rate notes are calculated on an actual/360-day account basis, while US Treasury bonds and notes are calculated on an actual/actual basis.
The fixed rate portion of the interest rate swap and most fixed rate bonds use either 30/360 or 30/365 days, while the floating rate portion uses some actual/360 or 365 day options. agreement.