闰年计算器

检查任意年份是否为闰年，查找下一个和上一个闰年，并列出自定义范围内的所有闰年。采用格里高利历三部分规则：能被 4 整除，但整百年须同时能被 400 整除。

Check a Year

2026 is not a Leap Year

365 days
Year2026
Leap Year?No
Days in Year365
Next Leap Year2028
Previous Leap Year2024

2026 is not divisible by 4 — not a leap year.

Leap Years in a Range

Found 13 leap years between 2000 and 2050
2000200420082012201620202024202820322036204020442048

Leap Years in the 2000s

All 25 leap years from 2000 to 2099. Click any year to check it above.

2000200420082012201620202024202820322036204020442048205220562060206420682072207620802084208820922096

常见问题

闰年的判断规则是什么？

格里高利历（公历）的闰年规则：①能被 4 整除的年份是闰年；②但能被 100 整除的年份不是闰年；③但能被 400 整除的年份是闰年。例如：2000 年是闰年，1900 年不是，2024 年是。

为什么需要闰年？

地球绕太阳公转一圈约需 365.2422 天，而日历年只有 365 天。每 4 年多出约 1 天，通过添加 2 月 29 日的闰年来补偿。精确的 100 年和 400 年规则进一步修正残余误差，使日历与天文年保持同步。

出生在 2 月 29 日的人如何庆祝生日？

出生在闰日（2 月 29 日）的人在非闰年通常选择 2 月 28 日或 3 月 1 日庆祝生日。法律上，不同国家/地区对闰日生日有不同规定，如部分地方在非闰年以 3 月 1 日作为法定生日。

下一个闰年是哪一年？

按闰年规则，您可以快速判断：如果年份能被 4 整除（且不能被 100 整除，或能被 400 整除），则为闰年。本计算器可显示任意年份范围内的所有闰年列表。

What is a Leap Year?

A leap year is a calendar year that contains an extra day — February 29 — making it 366 days long instead of the usual 365. Leap years exist to keep the calendar year synchronized with the solar year (the time Earth takes to orbit the Sun), which is approximately 365.2422 days. Without the occasional extra day, the calendar would drift about one day every four years, shifting seasons by weeks over a century.

Leap Year Rules — The Three-Part Algorithm

The Gregorian calendar uses three rules to determine whether a year is a leap year:

  1. Divisible by 4: If a year is evenly divisible by 4, it is a leap year — unless Rule 2 applies.
  2. Divisible by 100 (century exception): If a year is evenly divisible by 100, it is not a leap year — unless Rule 3 applies.
  3. Divisible by 400: If a year is evenly divisible by 400, it is a leap year regardless of Rule 2.

Algorithm in pseudocode:

isLeapYear(year):
  if year % 400 == 0  →  true   (e.g., 2000, 2400)
  if year % 100 == 0  →  false  (e.g., 1900, 2100)
  if year % 4   == 0  →  true   (e.g., 2024, 2028)
  else                →  false  (e.g., 2023, 2025)
Year÷4?÷100?÷400?Leap?
2024YesNoNoYes
2023NoNoNoNo
1900YesYesNoNo
2000YesYesYesYes
2100YesYesNoNo
2400YesYesYesYes

Why Does February Have 29 Days?

February is the shortest month in the Gregorian calendar, a legacy of ancient Roman calendar reforms. The original Roman calendar had only 10 months (304 days), starting in March. When King Numa Pompilius added January and February around 713 BC, he ended up with February as the last month with the fewest days — the Romans considered even numbers unlucky, so months alternated between 29 and 31 days except for February, which had 28.

Julius Caesar's calendar reform in 46 BC — the Julian calendar — introduced the concept of the leap day on February 29. February was chosen for the extra day because it was already the "overflow" month at the end of the Roman year. Pope Gregory XIII's 1582 reform kept February as the leap-day month but refined when it occurs to prevent long-term calendar drift.

Historical Calendar Background

The Julian Calendar (46 BC)

Julius Caesar introduced the Julian calendar, which added a leap day every four years without exception. This was a huge improvement over the chaotic Roman calendar, but because the solar year is slightly less than 365.25 days, the Julian calendar gained about 11 minutes per year — amounting to one full day every 128 years.

The Gregorian Reform (1582)

By 1582, the Julian calendar had drifted about 10 days ahead of the solar year. Pope Gregory XIII corrected this by skipping October 5–14, 1582 (October 4 was followed by October 15), and introducing the century exception: century years (1700, 1800, 1900…) are not leap years unless also divisible by 400. This reduces the average year to 365.2425 days — accurate to within 26 seconds per year.

The Century Exception Explained

The solar year is 365.24219 days. A simple "÷4" rule gives 365.25 days on average — too long by about 11 minutes. Removing three leap years every 400 years (the century years not divisible by 400) brings the average down to exactly 365.2425 days, a much better approximation. This is why 1900 was not a leap year but 2000 was.

Leap Year Frequency & Patterns

In a 400-year Gregorian cycle, there are exactly 97 leap years out of 400 — giving an average year length of 365.2425 days. The pattern is:

  • Most leap years occur every 4 years (e.g., 2024, 2028, 2032…).
  • Century years skip the leap day (e.g., 2100, 2200, 2300).
  • Every 400 years, a century year gets the leap day back (e.g., 2000, 2400).
  • The gap between two leap years is almost always 4 years, but can be 8 years around century years (e.g., 1896 → 1904, skipping 1900).

Leap Day Birthdays (Leaplings)

People born on February 29 are sometimes called leaplings or leap-day babies. Statistically, about 1 in 1,461 people are born on Feb 29 (roughly 0.068% of the population). Famous leaplings include motivational speaker Tony Robbins (born February 29, 1960) and rapper Ja Rule (born February 29, 1976).

In non-leap years, leaplings typically celebrate their birthdays on either February 28 or March 1, depending on cultural convention and legal jurisdiction. Some countries, such as the UK, legally recognize February 28 as the leap-day birthday in non-leap years.

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