Hello there! I'm a seasoned expert in the field of calendar studies, and I'm here to help you understand the fascinating world of leap years. A leap year is a year that is exactly divisible by 4, which means it has an extra day added to the calendar to synchronize with the Earth's orbit around the Sun.

The Gregorian calendar, which is the most widely used civil calendar today, is a solar calendar that aims to keep the date of the spring equinox close to March 21st. To achieve this, a leap year occurs every four years. However, there's a little more nuance to it. To account for the fact that the Earth's orbit is not exactly 365.25 days (which would make it simple), the calendar has a couple of additional rules:


1. Centennial Rule: If the year is evenly divisible by 100, it is not a leap year unless it is also evenly divisible by 400. This means that the year 1900 was not a leap year, but the year 2016 was because it is divisible by 400.


2. Leap Day: The additional day is added to the month of February, making it 29 days long instead of the usual 28. This day is known as February 29.

Now, let's talk about the identification of leap years. Here's a step-by-step guide to determining if a year is a leap year:

- Step 1: Check if the year is divisible by 4. If it is, proceed to the next step. If not, it's not a leap year.
- Step 2: If the year is a centennial year (ending in 00), check if it is divisible by 400. If it is, it's a leap year. If it's not, it's not a leap year.
- Step 3: If the year is not a centennial year, then if it passed Step 1, it is indeed a leap year.

Using these rules, let's look at a few examples:

- 2000: Divisible by 4 (2000 ÷ 4 = 500) and also divisible by 400 (2000 ÷ 400 = 5), so it's a leap year.
- 1900: Divisible by 4 (1900 ÷ 4 = 475) but not divisible by 400 (1900 ÷ 400 = 4.75), so it's not a leap year.
- 2016: As mentioned in your reference, it is a leap year because it is divisible by 4 (2016 ÷ 4 = 504) and also by 400 (2016 ÷ 400 = 5.04), making it a leap year.

It's important to note that the concept of leap years has evolved over time. The Julian calendar, introduced by Julius Caesar in 45 BCE, simply added a leap day every four years without the additional rules. This led to a discrepancy of about 11 minutes per year, which over centuries caused the dates of the equinoxes and solstices to drift from their original positions.

The Gregorian calendar, introduced by Pope Gregory XIII in 1582, corrected this discrepancy by omitting three leap days every 400 years, which aligned the calendar more closely with the astronomical year.

Now, let's move on to the translation of the above explanation into Chinese.

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2016 is a leap year, which means that it has 366 days instead of the usual 365 days that an ordinary year has. An extra day is added in a leap year--February 29 --which is called an intercalary day or a leap day.read more >>