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🐸 leap year checker

CHECK ANY LEAP YEAR

Enter a year to apply the Gregorian leap-year rules: divisible by 4, except century years unless divisible by 400. Range mode lists every leap year between two selected years.

Check a single year

Range start

Range end

1Divisible by 4?Most years pass here and earn their leap day—

2Divisible by 100?Century years lose the day… unless…—

3Divisible by 400?…the 400-year override restores it—

🌍 Why it existsThe true year is ~365.2422 days — 97 leap days per 400 years keep the seasons aligned.

📜 The 1582 fixThe Gregorian reform dropped 10 days (Oct 4 → Oct 15) and introduced the 4/100/400 rule.

🦄 Leaplings~5 million people born on Feb 29 — odds about 1 in 1,461.

💍 The proposal traditionIn some traditions, women proposed on Feb 29 — "Bachelor's Day" lore.

How to use this calculator

1Step 1Type any year — or a range to list all leap years in it.

2Step 2Watch the rule machine light up ÷4 → ÷100 → ÷400.

3Step 3Read the verdict, next/previous leap years and Feb 29 facts.

What the result includes

4/100/400 rule machine visual
Single year or range check
Leap-year chips for ranges
Next & previous leap years
Leapling facts & traditions

The 4/100/400 rule, step by step 🐸

Step 1: if the year divides evenly by 4, it's a leap candidate — otherwise it's a normal 365-day year and the machine stops. Step 2: if it also divides by 100, it's a century year, and the leap day is taken away. Step 3: unless it divides by 400, which hands the day back. Result: 2024 ✓ (÷4 only), 1900 ✗ (÷100 but not ÷400), 2000 ✓ (÷400), 2100 ✗, 2400 ✓.

Why the calendar needs this 🌍

Earth's orbit takes about 365.2422 days — not 365.25. A simple "every 4 years" rule would over-correct by ~0.0078 days/year, adding about 3 extra days every 400 years. The century exception removes 3 days per 400 years, leaving the Gregorian calendar drifting only ~27 seconds per year — a day every ~3,200 years. That's engineering.

Decision-path examples

Year	÷4	÷100	÷400	Verdict
2024	yes	no	—	LEAP ✅
2026	no	—	—	not leap
1900	yes	yes	no	not leap
2000	yes	yes	yes	LEAP ✅

Being a leapling 🦄

Born on February 29? You share a birthday with roughly 5 million people, and your odds of that were about 1 in 1,461. In common years, legal systems vary on whether your birthday falls February 28 or March 1 — but culturally, leaplings get to claim the whole day whenever it arrives. Our Age Calculator handles Feb 29 birthdays with full calendar respect, and the leap year deep-dive covers the history and traditions.

Sources & limits

The Gregorian leap-year rule is divisible by four, except century years unless divisible by 400.

U.S. Naval Observatory: leap years

Sources accessed: August 8, 2026.

🐸 FAQ

Is 2026 a leap year?

No — not divisible by 4. 2024 was the last one; 2028 is next.

What is the leap year rule?

Divisible by 4, except centuries, unless divisible by 400. 2000 ✓, 1900 ✗.

Why do leap years exist?

Earth orbits in ~365.2422 days; 97 leap days per 400 years keep seasons aligned with the calendar.

What are Feb 29 babies called?

Leaplings — about 5 million worldwide, odds ~1 in 1,461.

Can I check a range?

Yes — start and end year, and every leap year in between appears as a chip.

Why is 1900 not a leap year but 2000 is?

Century years are leap only when divisible by 400: 2000 passes, 1900 fails. The checker lights up each rule so you can see why.

How many leap years in a range?

Enter a start and end year and the checker lists every leap year in the range as chips, with the count.