FTB-C000712 / Financial concept

Day-count convention

A day-count convention defines how dates are converted into the time fraction used by an interest calculation.

Also known asday-count basis

Intermediate 3 linked topicsEvidence-reviewed

Definitions

In plain terms

Counting the same calendar interval under different denominators or boundary rules can produce different interest.

Technical

The selected D30 Actual/365 Fixed example uses its counted actual days divided by 365; other conventions require their own leap-year and interval rules.

Scope

Actual/365 Fixed, Actual/Actual and 30/360 are not interchangeable labels.

Examples

  • For the declared Actual/365 Fixed profile, ten counted days contribute a year fraction of 10/365.

Common misconceptions

  • A rate described as annual does not identify the day-count convention.

Concept relationships

Related

Where this concept is used

Evidence and governance

  1. Derivatives User Guide, Oracle Banking Treasury Management 14.5.3.0.0, pages 36–37 Oracle · official platform documentation

    Supports: preferred label, short definition, variant distinction

    Limits: A named historical product guide, not a current derivatives contract or deposit-account mandate; D30 date boundaries remain authored choices.

  2. D30 glossary teaching-profile scope, Batch 013 The Fintech Builder · internal governed contract

    Supports: technical definition

    Limits: No independent regulatory mandate, real-bank dataset, service execution, external witness or production assurance is claimed.

Reviewed by
fintech-builder-batch-013
Last reviewed
2026-10-27
Next review
2027-10-27
Record status
evidence reviewed

This record is evidence-reviewed and readable, but not yet promoted to published — it is served noindex,follow and excluded from the sitemap.

Written by

Fintech engineer building market-data and financial systems, and the author of every article, glossary record, and reference implementation on The Fintech Builder.