Until 1873, Japan used a method of date keeping called the lunisolar calendar that, if we look at the word lunisolar, implies it is a lunar and solar calendar. The moon and the sun.
Despite on-going issues between Japan and China, the lunisolar calendar was indeed a Chinese invention, and had been used by the Japanese since about the 7th century.
Are you ready for some tricky stuff?
Depending on the country that uses a version of the lunisolar calendar, it can be used to: indicate the moon phase and the time of the solar year (also known as a tropical year - which is about a standard year - less 20 minutes).
So... a lunisolar calendar following a solar/tropical year, will show the observer the 'season'... which you could probably guess anyways if there is someone trying to throw a snowball down your chest.
So (again)... a lunisolar calendar that follows the sidereal year (time taken by Earth to orbit the Sun once with respect to fixed stars... just know that it is 20 minutes and 24.5128 seconds longer than a tropical year). Essentially, this give you your planet's position amongst the constellations of the full moon.
What the hell does this all mean? I have no clue.
Japan really did follow a lunar calendar.
In the old days, Japan had years of 12 months of 30 days, and to make up the need to have a proper year cycle involving 365.25 days (the quarter day is why there is an additional day in February - the 29th, every four years in the Gregorian calendar), Japan would add a 13th month every few years or so.
Since the lunar calendar follows the moon's cycles, it was actually five whole days shorter than the solar calendar.
As such, the Japanese calendar added a 13th month every six years - to catch up. This extra month in the lunar calendar is called the 'intercalated' month.
While the lunar calendar was good for the average Japanese person, it wasn't so good for the average Japanese farmer who need an accurate measure of when to prep and plant the crops and when to harvest. A lunar calendar in the fifth year of the cycle was going to put the whole planting and harvesting thing over by 25 days or more.
So... the Japanese farmer used the old Chinese calendar - a solar calendar - developed by Chinese astronomers. This lunar calendar is actually called a koyomi.
This solar calendar (koyomi) measured between two successive Winter Solstices. The winter solstice was the mid-point of twelve equal divisions called setsu which were approximately 30.44 days in duration.
The Japanese would divide each setsu in half... a beginning point called a sekki, and a mid-point called a chuki. This makes 2 units within each of the 12 setsu... meaning there are a total of 24 sekki and chuki.
Each of these 24 units had a name related to weather or agriculture. For example... the beginning of February is the New Year - Spring; the beginning of May is Summer; the beginning of August is Autumn; and the beginning of November is Winter.
I state 'beginning' rather than an actual date, because it changes. It's why the so-called Chinese New Year is on a different date every year.
So... Japanese farmers used the solar calendar. The rest of Japan used the lunar calendar. That's why Japan's calendar system was a lunisolar calendar.
Now... here's where it get's more bizarre. Since Japan's months were based on 30 days, the regular non-farmer Japanese people would divide the 30 days into three parts.
The first 10 days of the month were known as jojun.
The middle 10 days of the month were known as chujun.
The last 10 days of the month were known as gejun.
Got it? So far so good.
Now... just because it's Japan, and Japan likes to make things more complex than it needs to be, each month of 30 days is made up of five weeks consisting of six days each.
That's right... the Japanese week was six days long. The collection of six days - a Japanese week - was known as a rokuyo.
These six days, in order, are: Sensho, Tomobiki, Senbu, Butsumetsu, Taian, and Shakko. Shakko was my favorite member of the Three Stooges. That's a joke.
And you think that would be it, but no... Even after this Japanese calendar was replaced by the Gregorian calendar in 1973, a group of people kept it up.
These people are Fortune Tellers. And, if you think that is weird, just remember... pretty much all of you readers know if you were born a Scorpio or a Virgo. You know who you are.
Anyhow, the fortune tellers used the rokuyu terms and days and gave fortune-telling meanings to each day.
I know... you are curious. That's part of your birth sign. Me... I'm a Scorpio male born in the Year of the Dragon... and not just any dragon, but I'm a Wood dragon. Who's got wood? I do.
Let's look at each day's fortune or mis-fortune:
Sensho (also known as sakikachi, senkachi and sakigachi) is a good day for urgent tasks and lawsuits. It brings good luck in the morning, but bad luck between 2PM and 6PM. Seems to me 2PM to 6PM is a great time to take a nap.
Tomobiki is a day to avoid deciding or settling things. But, it's good luck in the morning, bad luck in the afternoon, and very good luck in the evening. Again... nap time in the afternoon to avoid the crap luck.
Senbu (also known as senpu, senmake and sakimake) was supposed to be a lucky day, but some consider it a bad day for settling things like lawsuits. WTF? What's with all of the lawsuits in old Japan? As well, there's bad luck in the morning and good luck in the afternoon. Maybe they should avoid settling a lawsuit in the morning.
Butsumetsu is an all around bad-luck day. Great. If that's true, no one should work or settle a lawsuit. This is another day where weddings and other celebrations are avoided. And the crap part about this, is that it occurs five times a month, 12 or 13 times a year... for 60 or 65 really crappy bad luck days. Geez, Japanese fortune tellers... way to spread out the bad luck.
Taian (also called Daian) is the luckiest day of the week, and thus a great day to get married or celebrate the survival of yet another unlucky day. This may also have been a day of rest (like the West's Sunday) because everyone was off celebrating.
Shakko (also known as jakku, shakku, jakko and sekiguchi) is yet another unlucky day, with only the hours of 11AM and 1PM being lucky.
Wow... it must have sucked to believe in the fortune telling back then (or now, seeing as how it is still used).
Anyhow... back to the non-fortune telling part of this blog. On a lunar calendar, January and July start with Sensho; February and August with Tomobiki; March and September with Senbu; April and October with Butsumetsu; May and November with Taian, and; June and December with Shakko.
And here's something I bet you didn't know! From the years 862AD until 1683AD, the Japanese calendar was arranged so that a full moon always occurred the 13th day of each month. Since I'm guessing the Japanese had no notion of The Knight's Templar being attacked by forces consisting of the French and a jealous Pope on a Friday the 13th in 1307, 13 wasn't considered an unlucky number... such lunacy.
In 1684, when the calendar was changed so that a NEW MOON could land on the first day of each month, it pushed a FULL MOON appearance back two days later to the 15th of each month.
This was important, because Japanese people liked to do tsukimi - moon viewing.
So ... aside from learning something about something you never, ever thought to examine, what else have we learned? Well... from a purely selfish point of view, I'm glad that this lunisolar calendar has essentially gone the way of the Japanese River Otter. What? Too soon?
Twenty-four hours from now, in yet another senses-shattering blog, I'll present the calendar systems that replaced the lunisolar calendar. Yes... I pluralized the word 'system'. Pluralized because simply having one single way to count the years is just too simple a thing for Japan.
As for the image above, it's an 1893 ukiyo-e print depicting a ryakureki - a single-page calendar. As you can see... it's as big as a man and still a bitch to read!