There Are Two April Fools' Days This Year. No, Really.

Original Zeus Zou theBeijinger

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It can be pretty difficult to get people to agree on just about anything these days. Between alternative facts and fake news, everyone seems to be living in a reality of their own construction. Even still, there are a few indisputable details that even the most contrarian among us can't deny. For example, I think we can all agree that we're currently in the final days of May, which will inevitably give way to June and another blazing Beijing summer... right?

Wrong! Or at least you would be if you live solely by China's lunar calendar, which will tell you that today is only the fifth day of the fourth lunar month (or what would be Apr 5, 2020 according to the Gregorian calendar). Don't worry, you haven't slipped into the Twilight Zone – there is merely a parallel timeline existing alongside this one, and it's called the Chinese agricultural calendar.

If your head is spinning, let's see if we can't clear a few things up.

A good place is by clarifying some commonly misunderstood facets of China's calendar. For instance, the "lunar calendar" is generally used synonymously with the traditional Chinese calendar, so much so that Spring Festival has been dubbed Lunar New Year. However, this is technically wrong. There are three major types of calendars around the world: the solar calendar (the Gregorian), the lunar calendar, and one that combines the two, creatively called the lunisolar calendar. And despite what celebrating the Lunar New Year might have you believe, the traditional Chinese calendar is actually based on the latter calendar.

The invention of a bonus lunar month was inspired by the moon's orbital movements

So what exactly is the difference, you ask. Well, while the solar, or Gregorian calendar that most countries use today, is based on the number of days that the Earth takes to revolve around the sun, the lunar calendar is derived from the amount of time the moon needs to orbit around Earth. As a result, the Gregorian calendar reflects the changing seasons, and its number of months and their duration is flexible, while in the lunar calendar, the length of each month is uniform, meaning you can fit as many months as you like into a year. However, what the lunar calendar lacks in marking seasonal transitions, it more than makes up in its ability to predict tidal variations and the waxing and waning of the moon.

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So what happens when you want the best of both worlds? If you're the ancient Chinese, you simply combine both calendars to make the traditional Chinese calendar, 农历 nónglì lit. agricultural calendar. The lunisolar calendar thus caters to the needs of farmers, who were keen to know when their crops would be dry and when they would be wet, regardless of solar seasons. Like other lunisolar calendars, the traditional Chinese calendar gives months a determined length based on the moon's orbit. In order to keep the length of a year commensurate with the amount of time needed for the Earth to circle the sun, however, ancient Chinese astronomers created the 闰月 rùnyuè, or bonus month, a clever workaround for their cosmic dilemma.

Now this is where you really need to pay attention. Since the moon orbits the Earth every 29 or 30 days (technically 29.5), each month in the traditional Chinese calendar reflects one full moon cycle, with shorter 29-day cycles called "little months" and longer 30-day cycles called, well, "big months." Moreover, every time a crescent moon appears in the night sky, it marks the beginning of a new month. With 365 days in a year and one crescent moon on average every 29.5 days, you're left with 12.37 lunar months in a year. Therefore, so as to ensure that the calendar continues to align with the changing of the seasons, the ancient Chinese added an extra lunar month the calendar every three years (or so). Why "or so?" Well, to get into that as well as which month is added could fill another entire blog by itself, and potentially leave you questioning the very essence of time itself.

Finally, most of China only celebrate festivals that fall during the regular, non-make-up months. Saying that, if the 12th month happens to be the bonus month, then its last day will be considered the end of that year.

So what does having two fourth lunar months mean for 2020? Funnily, it means that come October, we'll be able to celebrate Mid-Autumn Festival (the 15th day of the eighth lunar month) on the same day as National Day, Oct 1.