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Time & DateGenerated accuracy model review: 2026-05-06
Leap Year Check accuracy and testing
This page documents how Calwarden builds trust for this calculator: source notes, regression-style default tests, limitations, assumptions, unit handling, rounding, and visible change history.
Formula source
- The logic for the Gregorian calendar is: 1. If the year is divisible by 4, it is a leap year. 2. **UNLESS** it is divisible by 100, then it is NOT a leap year. 3. **UNLESS** it is also divisible by 400, then it IS a leap year.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- Year: 2,026
Expected outputs
- Is Leap Year?: No
- Days in Year: 365
Known limitations
- This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
- Use the result as a planning estimate unless the calculator page states a stricter purpose.
Assumptions
- The logic follows the Gregorian leap-year rule used by modern civil calendars.
- Years divisible by 4 are leap years unless they are century years not divisible by 400.
- This tool checks the year-level rule only and does not account for historical calendar adoption differences by country.
Unit handling
- Year accepts numeric values.
Rounding rules
- Number displays use up to 2 decimal places in the calculator UI.
Version history
1.0.0 - 2026-05-06
Generated accuracy and testing page from the current leap-year-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for Leap Year Check.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.