Most of us are good about knowing what the current year is (at least, once you get past the first few times in January where you write the previous year’s numerals out of habit). But what about cultures and religions that follow more than one calendar cycle?
For business and legal reasons, most of the world uses the Gregorian calendar, which was introduced by its namesake, Pope Gregory XIII, in 1582. By the Gregorian calendar, it is the year 2020. But there are many other calendars currently in use. You’re undoubtedly familiar with a few of them, even if you don’t know how they work (like why does the Chinese New Year always fall in late January or February?). If you’ve ever wondered how and why these different calendrical systems vary so greatly, read on.
There are three main calendar systems: lunar, solar, and lunisolar. The Gregorian calendar is solar, meaning it's based entirely on the position of the Sun. The Hebrew calendar is lunisolar. That means that months are based on lunar months and years are based on solar years. The Hebrew calendar is mostly used to determine Jewish holidays (which is why Hanukkah, Rosh Hashanah, and other important observations aren't on the same dates each year), and it's among the oldest calendars still in use.
Jewish days begin at sunset and end the following sunset, which means that they don't last a predetermined amount of time. This is based on a line from Genesis 1:5: “There was evening and there was morning, one day.” Hours aren't of fixed length either, as they're defined as 1/12th of the time between sunrise and sunset; though most will therefore last around 60 minutes, they may be shorter in winter and longer in summer.
The calendar gets really interesting when you start calculating months and years. There are usually 12 months of either 29 or 30 days — Nisan, Iyar, Sivan, Tammuz, Av, Elul, Tishrei, Cheshvan, Kislev, Tevet, Shevat, and Adar — for a total of 353, 354, or 355 days (Cheshvan and Kislev can both last either 29 or 30 days). However, seven out of every 19 years feature a leap month to ensure that Passover always takes place in spring. The extra month, known as Adar I or Adar Aleph ("first Adar"), takes place before Adar and has 30 days.
The current year is 5780, which according to the calendar means that's how long it's been since the world was created (Anno Mundi). Most years begin on Rosh Hashanah, which translates as “the head of the year.” But there's a catch there as well: Years can only begin on four days of the week (Monday, Tuesday, Thursday, and Saturday).
The Chinese calendar is also lunisolar, with each month lasting 29.5 days — the amount of time it takes for each New Moon. Because dividing days in half is neither easy nor practical, odd months (first, third, etc.) have 30 days and even months (second, fourth, etc.) have 29 days. This is easier to remember than many other calendrical systems since it means that each month starts on the same day as the New Moon — but there is a complication. Since it only adds up to 354 days, there’s a leap month every three years to account for that 33-day disparity.
China itself uses the Gregorian calendar, but its traditional calendar (also known as the Agricultural Calendar, Former Calendar, and Lunar Calendar) determines holidays. The most famous of these is Chinese New Year, which is called the Spring Festival domestically and takes place in January or February. There's also the 12-year Zodiac cycle, of course; it’s currently the year of the Gold Rat.
The Armenian calendar is exactly 365 days and does not use leap years, meaning it gradually drifts further away from the Julian (the main calendar in use when it was first adopted) and Gregorian systems. All 12 months — nawasard, hoṙi, sahmi, trē, kʿałocʿ, aracʿ, mehekan, areg, ahekan, mareri, margacʿ, and hroticʿ — have exactly 30 days. Any mathematicians reading will have noticed that that only adds up to 360, which is why there are also five aweleacʿ (“superfluous”) days tacked on at the end.
In a somewhat confusing set lineup of years, the first day of the Armenian calendar began on July 11, 552, of the Julian calendar. When the switch from Julian to Gregorian happened in 1582, the Armenian calendar kept going on its cycle. The current year according to the Armenian calendar is 1469.
The Democratic People's Republic of Korea calendar, also called the DPRK calendar and Juche calendar, is one of the simplest in the world. According to the calendar, it’s currently the year Juche 109, as Kim Il-sung was born on April 15, 1912, and his birthday marks the first day of the year. Kim, who founded the country and ruled it until his death in 1994 (his grandson Kim Jong-Un is now Supreme Leader), is far and away the most revered figure in North Korea. His birthday is celebrated as Day of the Sun and is considered the country's closest equivalent to Christmas.