Instantly test any year using modern validation tools. Scan ranges or pasted lists in seconds. Download clean reports for documentation, teams, and compliance needs.
| Year | Expected | Why |
|---|---|---|
| 1996 | Leap | Divisible by 4, not by 100. |
| 1900 | Common | Divisible by 100, not by 400. |
| 2000 | Leap | Divisible by 400. |
| 2024 | Leap | Divisible by 4, not by 100. |
| 2025 | Common | Not divisible by 4. |
Gregorian rule: Leap years are divisible by 4, except century years must be divisible by 400.
Julian rule: Leap years are simply divisible by 4.
The checker applies the Gregorian 4/100/400 rule, which yields 97 leap years in every 400-year cycle and an average year length of 365.2425 days. When the Julian option is selected, the rule is simpler: every year divisible by 4 is a leap year. This calculator reports both the decision and the exact rule branch used in production and classroom demos.
Single mode accepts a year directly, or derives the year from a date, datetime, or Unix timestamp using a selected timezone. Range mode scans start-to-end years inclusively with a safety limit of 5,000 years per run. Bulk List mode ingests comma, space, or newline separated values, de-duplicates them, sorts them, and caps runs at 2,000 unique years.
Inputs are parsed as signed integers from -9999 to 9999, with server-side checks for empty values and non-numeric characters. Range validation enforces start ≤ end and blocks oversized runs to protect server resources. Edge cases are surfaced in the “Reason” text, especially century years like 1900 (common) versus 2000 (leap) under Gregorian rules.
For Range and Bulk List outputs, the tool totals leap years and common years, then visualizes the split using an interactive Plotly chart. Over a long Gregorian horizon, leap years occur about 24.25% of the time (97/400), so large ranges should approach that share. The displayed table supports quick filtering, while the chart provides a fast distribution check for QA and reporting.
CSV export produces structured rows (Year, Calendar, Leap, Reason, Source) suitable for spreadsheets, CI artifacts, or audit folders. PDF export generates a lightweight, single-page report containing run metadata, a summary line, and up to 200 result rows before truncation. These exports help keep change logs consistent across environments.
Computation is O(n) over the number of evaluated years, so typical runs complete quickly even at the 5,000-year limit. Recommended regression cases include 1600 (leap), 1700 (common), 2000 (leap), and 2100 (common) for Gregorian, plus any year divisible by 4 for Julian. Pair the CSV output with automated tests to detect rule regressions.
1) Which calendar rule should I select?
Use Gregorian for modern civil dates and software systems. Choose Julian only for historical workflows or domain models that explicitly use the Julian leap rule.
2) Why is 1900 not a leap year?
Under Gregorian rules, years divisible by 100 are common unless also divisible by 400. Since 1900 % 400 ≠ 0, it is treated as a common year.
3) Can I check a date or timestamp?
Yes. In Single mode you can enter a date, a datetime, or a Unix timestamp. The tool converts it to a year using your selected timezone, then applies the chosen calendar rule.
4) What size limits are enforced?
Range runs are limited to 5,000 years per submission. Bulk List runs are limited to 2,000 unique years after de-duplication and sorting.
5) Does timezone change the leap result?
Timezone matters only when deriving a year from a datetime or timestamp near year boundaries. For direct year input, timezone does not affect the leap calculation.
6) What is included in CSV and PDF exports?
CSV provides structured rows for every computed year, ideal for analysis. PDF generates a compact report with run metadata and up to 200 rows, then truncates to keep the file lightweight.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.