Day Count Convention Calculator
Compare Actual/360, Actual/365, Actual/Actual and 30/360 U.S. year fractions for two dates. Inputs stay in your browser.
ACT-360 day-count result for the entered dates.
Context matters.
- Financial contracts can specify different endpoint, end-of-month and leap-year rules. The exact instrument terms control.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Compare Actual/360, Actual/365, Actual/Actual and 30/360 U.S. year fractions for two dates. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Start date, End date and Day-count convention supplied in the form.
- Apply the scope. It applies the Financial date arithmetic — exact instrument definition and jurisdiction control reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
ACT-360 day-count result for the entered dates.
- Year fraction0.08333333
Calculation purpose: Compare Actual/360, Actual/365, Actual/Actual and 30/360 U.S. year fractions for two dates. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Calendar inputs use plain year-month-day semantics. Leap days, month ends, date-pair order and unsupported dates are checked before the result is shown.
Rule set 1.1.0 · Last reviewed 2026-08-20 · Next review due 2027-02-20. The source panel below contains the linked evidence.
What to know before using the result.
Why do ACT/360 and ACT/365 give different fractions?
Both use actual elapsed days in the numerator but divide by different fixed year bases.
What does 30/360 do?
It applies a standardized 30-day-month convention rather than counting every actual calendar day.
Which convention should I use for a contract or security?
Use the convention stated in the controlling agreement or instrument. CalcSpan compares arithmetic conventions but does not choose the legal one for you.