六曜 ROKUYO – Lucky and Unlucky Days in Japan

Japanese people are perhaps not as superstitious as many other Eastern people, such as Burmese, and no more superstitious than many Westerners. In fact some Western superstitions are so strong that they are exported to other cultures. Take for example Friday 13th.

For the Japanese, Friday 13th is just one of several unlucky days. The number 4 is unlucky because a Japanese pronunciation of 4 is similar to the word for 'death'. Therefore 4 April is unlucky (4th day of 4th month). On the other hand, just as seven is considered a lucky number in most cultures, in Japan 7 July and 8 August are considered lucky. In fact for the Japanese every single day is associated with luck, misfortune or something in between. Delicate planning is required to make sure important occasions happen on the 'best' day.

This page explains Rokuyo – the lucky and unlucky days of the Japanese Calendar, and discusses its impact on weddings, hospital stays, funerals, baby booms and doing business in Japan.

Note: This page is for information only.
We are not trying to promote Rokuyo;
in fact we don't believe any of it!
Here's why.


The Days of Rokuyo

The history of the Japanese calendar is fascinating. Since 800 AD Japan has used a seven day week with names for the days corresponding directly with those used in Europe. This system was used for astrological purposes and little else until 1876, shortly after Japan officially adopted the Western calendar.

The seven day names were simply from the Chinese philosophies of yin-yang, plus the five classical Taoist elements: fire, water, wood, metal and earth.

  • Sunday - nichi-youbi (yang - sun)
  • Monday - getsu-youbi (yin - moon)
  • Tuesday - ka-youbi (fire)
  • Wednesday - sui-youbi (water)
  • Thursday - moku-youbi (wood)
  • Friday - kin-youbi (metal/gold)
  • Saturday - dou-youbi (earth)
Yang and Yin

(Sun & Mon)
5 elements
5 elements
(Tue –s Sat)

Although the seven days have been used in Japan for around 1,200 years, until the 19th century they also had a parallel six-day system, which had more effect on daily life than the seven-day astrological system.* The six days were known as Rokuyo (roku - six, yo - day) and were based on superstition of good and bad luck. Rokuyo no longer forms part of the official calendar in Japan, but it can still often be seen in small print on calendars and diary pages.

Each Rokuyo day has a name and an associated meaning:

  • 先勝 – Sensho (also known as Senkachi or Sakigachi)**

    Good luck in the morning, bad luck in the afternoon. A good day for starting new ventures and dealing with urgent business.

    It is also favoured for success in sporting events, yet for most matches there are winners and losers. So for a win-win situation, the sporting event should be something like breaking a personal-best record running a marathon or lifting a heavier weight.

    Sensho is also favoured for those summoned to appear court, but again, in many cases there are victims and perpetrators. A win-win situation could be a successful acquittal of a so-called 'victimless crime' or an amnesty from a crime that society now agrees is outdated and should be abolished.

  • 友引 – Tomobiki

    Good luck all day, except at noon. The kanji literally translated means "pulling friends".

    Not considered a good day for winning at a sports match, since sports are best enjoyed when playing with friends. In the spirit of sportsmanship a player wants their opponent to enjoy the game, even if that means letting the opponent win.

    Tomobiki is a good day for a wedding, where you can pull your friends into the spirit of love. However, since the end of the Edo period, Tomobiki days are avoided for funerals, where your friends might be pulled to the "other side".

  • 先負 – Sakimake (also known as Senmake or Senbu)**

    Bad luck in the morning, good luck in the afternoon. Better not start any new venture until after noon.

    Urgent business should be deferred until later in the day, as should attempting to settle disputes and public affairs.

  • 仏滅 – Butsumetsu

    Unlucky all day, because it's the day Buddha died. Best to avoid doing anything important on this day.

    Life is full of important events and some give no control over scheduling. But non-urgent medical check-ups can be deferred for a day, as can moving house, opening a new shop, having a wedding ceremony, etc.

    Some people believe that if you become ill on a Butsumetsu day, the illness will last for long time.

  • 大安 – Taian

    The kanji means "great peace". This auspicious day is the finest for wedding ceremonies, starting new business ventures, having success with love, exams, etc.

    Also a good day for surgery, starting building projects, moving house, travel, etc.

  • 赤口 – Shakku (also known as Shakko or Jakko)**

    Bad luck all day except at noon. The kanji literally means "red mouth" and a caution to carpenters, chefs, etc., who use knives. The red symbolises blood and fire, so fire-eaters should take care also!

* A six-day system would be nicer than our seven-day week – We could abolish Mondays!

** For most Japanese people the only notable days are Tomobiki, Butsumetsu and Taian. The other three days are less often referred to, hence their non-standardised transliterations.

Noon - an important feature in Rokuyo

We normally consider noon to be 12:00 p.m. — that instant between morning and afternoon.

Now as you know, an instant is so infinitesimally small that philosophers and mathematicians since Aristotle have puzzled over what an instant is, how to measure it or how to observe what happens in it. But don't worry; you don't need to crawl to a quiet corner to contemplate all this, since the Rokuyo "noon" lasts for two hours; from 11:00 a.m. until 1:00 p.m.

In Japan, as elsewhere, the day used to be divided into 12 rather than 24 hours. This 12-part Zodiac influenced old religions and cultures, not only throughout a duodecennium (12-year period), but also throughout each day. Each temporal unit of a day was associated with one of the 12 animals of the Japanese zodiac:

Modern timeZodiac animal – Formal name (Common name)Hour***
23:00-01:00Mouse*Shi (Ne, Nezumi)九 9
01:00-03:00OxChū (Ushi)八 8
03:00-05:00TigerIn (Tora)七 7
05:00-07:00Rabbit, HareBð (U, Usagi)六 6
07:00-09:00DragonShin (Tatsu, Ryū)五 5
09:00-11:00SnakeShi (Mi, Hebi)四 4
11:00-13:00HorseGo (Uma)九 9
13:00-15:00Sheep, Ram, GoatBi (Hitsuji)八 8
15:00-17:00MonkeyShin (Saru)七 7
17:00-19:00Cock**Yū (Tori)六 6
19:00-21:00DogJutsu (Inu)五 5
21:00-23:00Boar, PigGai (I, Inoshishi)四 4

So noon is the hour of the horse (Uma no koku).

Edo period clock

Unlike the normal kanji for a horse (馬), the zodiac horse is assigned the kanji 午, which is similar to 牛, the kanji for a cow. This might be why he's a bit feisty, resulting in the change of pace for each Rokuyo day – except Taian and Butsumetsu, which are presumably the horse's days off.

* The rodent may be a mouse or rat, depending on whether we're thinking of a pet or a pest. In Japanese the kanji for rodent is used.

** Cockerel or rooster, depending on whether we're using British or American English.

*** The hour number started at 9, the highest mark etched on an incense stick, which burned for six hours down to 4. A new stick was then used for the next six hours. The counting started at 9, a Chinese homophone of the word for 'long lasting', followed by 8, 7, 6, 5 and 4, being the least significant digits of incremental multiples of 9, where:

  • the 1st period is 9 (1 x 9 = 9)
  • the 2nd period is 8 (2 x 9 = 18)
  • the 3rd period is 7 (3 x 9 = 27)
  • the 4th period is 6 (4 x 9 = 36)
  • the 5th period is 5 (5 x 9 = 45)
  • and 6th period is 4 (6 x 9 = 54)

The digital root of each multiple is also the cosy 9, a phenomenon unique to the number 9.

This quaint system was superseded by the Western method of timekeeping in 1873 and doesn't feature in any Japanese customs today; unlike Rokuyo, which is withstanding the test of time.

How Rokuyo days are calculated

The days basically follow the cycle from Sensho to Shakku, as listed above.

There are exceptions; the first days of months in the old Chinese lunar calendar are always assigned the same Rokuyo day:

Lunar monthFirst day
1 and 7先勝 – Sensho
2 and 8友引 – Tomobiki
3 and 9先負 – Sakimake
4 and 10仏滅 – Butsumetsu
5 and 11大安 – Taian
6 and 12赤口 – Shakku

If you want to calculate Rokuyo days for yourself, one way is to learn the Japanese language and study one of the many Japanese webpages that explain it.

But if you don't want to spend years learning Japanese then here's an important point to remember: Rokuyo was invented to give people like you and me a headache. The complicated calculation alone is evidence that somebody, years ago, thought: "Let's have some fun and set a mental time-bomb (a temporal temporal bomb) for foreigners, hundreds of years from now."


The six-day cycle is not regular; as you see in the table above the cycle is reset at the start of each lunar month. Why? Who knows, but that's what it does. And if you remember from junior school, the average length of a synodic month is 29.530589 days. And that means two things:

  1. Some months are 29 days, some are 30, and we throw in an extra day from time to time to smooth things out.
  2. They teach us some awesome stuff at school which we thought we'd never need. How wrong we were.

The first day of a lunar "month" is the day when an astronomical new moon occurs in a particular time zone, and that introduces other problems (as they say in Japanese Naki-ttsura ni hachi*): Should we calculate using Japanese time or GMT? Or since the calendar originated in China, precisely which longitude applies?

A new moon appears on the same day world-wide, so the Japanese and Chinese lunar calendars are pretty much the same. However, a lunar "month" is not a precise number of earth days, ranging 29 days 8 hours to 29 days 19 hours. This is rounded up or down to 29 or 30 days, corresponding to the period of lunation. For regions at different longitudes (China and Japan, for example) and as different cultures used different astronomical data, a different day could be calculated as the start of the lunar month.

Over the centuries methods of calculation improved in both Japan and China, but Japanese improvements tended to lag behind those of China. So at some periods, there were marked differences between the two calendars. Complicating matters further, a leap month was added every few years to keep the calendar aligned with the seasons and soltices.

For today's calculations of Rokuyo, having decided which lunar calendar to use, it's then a simple case of first superimposing it over our current Western calendar (with its different number of days each month: 28, 29, 30 or 31), and then reaching for an aspirin to soothe our nerves.

Focus too much on the 'time' thing and we risk drifting into the esoteric nature of this indefinite and irreversible succession of things and events from the past through the present to the future, start chanting weird things and get taken away by men in white coats.

Fortunately there's no need for you to calculate this for yourself at all, because we publish the Rokuyo for every day of the years 2000 to 2050 here.

* Naki-ttsura ni hachi = You're already crying, and then a bee comes along and stings you.

Better Safe than Sorry

In January 1873, despite the turmoil going on at the time, Japan changed from the lunar system to the solar (Gregorian) calendar system as part of their plan to trade more easily with the West.

In addition to adopting the Western calendar, they changed the length of the 'hours'. This was an incredibly brave move and something that few would seriously contemplate today (except perhaps proponents of the Metric or Decimalized Time system).

Before 1873 Japan used an interesting time system based on a 'day' starting at dawn, and a 'night' starting at sunset. The 'day' was sub-divided into six equal-length 'hours', and the 'night' was sub-divided into six equal-length 'hours'. As the seasons stretched the days or nights, the length of these 'hours' constantly changed. Accurately altering the regulator on early clocks every couple of weeks was a nightmare and was quite a challenge for the early clockmakers. (Did people really use their pulse for finer time-measurement? *) All that changed in 1873, and a few years later, young Kintaro Hattori established K Hattori & Co., Ltd., the forerunner of what became the Seiko Corporation.

These exciting developments made little difference to most people however; farming continued to be governed by the unofficial yet ancient solar calendar developed by Chinese astronomers, the seasons and the weather. And of course trains on the newly opened Tokyo to Yokohama rail link ran on time.

For its international commercial image however, changes made by people such as Hattori brought Japan right up to date with the rest of the world.

But the superstitions based on 'time' remained. Few Japanese would admit to serious belief of the system now, but a Pascalian 'better be safe than sorry' attitude is common when arranging things. (See also superstitions)

* Probably not. See A 60-second guide to 60 minutes

Lucky Days for Births

When attempting to make a baby, Rokuyo is not known to be an effective 'marital aid'.

The evidence of any Rokuyo effect on birth delivery days is thin and unlikely to feature much in the parents' decision making. Only a fool would risk messing about with nature by relying on superstition; it goes against natural human behaviour to put one's offspring at risk.

To trust an ancient custom with a dodgy reputation would be to say that Rokuyo had miraculous powers, and it is commonly accepted that miracles are the working of a divine power. If you feel that Rokuyo or astrology is divine, then you are missing out on something infinitely more wonderful.

Until recently, deciding on which day a baby is born has not been possible. But with the advent of induced labour, there is a slight tendency for some parents to request delaying birth by a day or two, or hastening it, to avoid Butsumetsu or to coincide with Taian. Doctors naturally discourage such approaches.

This happens not only in Japan but all across Asia. In Taiwan for example, a study in 2003* showed increases in deliveries on auspicious days and decreases on inauspicious days according to the Chinese lunar calendar. However, in the vast majority of cases the joy of having a baby, plus the emotional strain, don't leave much time for parents to consider Rokuyo very much, if at all.

Rather than the parents deciding the delivery date, their doctor, who is ever mindful of the necessity to have happy parents rear a child, will always advise that the best day is the day decided by the baby. With the advances in medicine it may be possible in the future to have such designer births with no risk to the child. Whether this will happen before the Rokuyo system fades from Japanese culture remains to be seen.

Having said all that, making such decisions may be a waste of time. In 2011 researchers at Yale School of Public Health examined 1.8 million US birth certificates over an 11-year period and found that birth rates dropped by 11% on spooky Halloween, when compared with one week on either side of the date. This applied to both 'natural' and induced births. They also noted a 3.6% increase in spontaneous births and a 12.1% increase in cesarean births on Valentine's Day. The study suggested that a psychological influence over hormonal activity may be at work.**

* Patients' attitudes vs. physicians' determination: implications for cesarean sections (Soc Sci Med. 2003 Jul;57(1):91-6)

** Influence of Valentine's Day and Halloween on Birth Timing (Social Science & Medicine, DOI: 10.1016/j.socscimed.2011.07.008)

Lucky Days for Weddings

Traditionally Taian and Tomobiki are the most popular days to tie the knot and Butsumetsu is the least favoured. However, in the current uncertain economy, money has become a significant factor in deciding the best day for a wedding in Japan.

Due to the passing of the baby boom of 25-30 years ago, fewer people will reach the marrying age for the next generation or so. Therefore wedding companies face the double problem of a shrinking market and an economy that has been weak since the 90s.

In response, many companies today are offering a special discount to people who use their services on a Butsumetsu day. This incentive has had the effect that the peaks and troughs seen in a typical wedding week a few years ago are now levelling off. The cost of offering the incentive is more than made up by the efficiency gained in the more balanced use of resources throughout the week.

Those who choose to marry on a Butsumetsu that's also Friday the 13th, are more likely interested in saving money, rather than being superstitious.

(See also Lucky Horseshoe and Western-style Weddings in Japan)

Lucky Days for Funerals

Rokuyo has no part to play in the timing of death. In special cases, death can be scheduled; for example when the life-support equipment or medication is withdrawn from a terminally ill patient, or for prisoner execution, murder or suicide. There is clearly no place for superstition in any of such scheduling.*

For funerals, however, a ceremony on Butsumetsu may give the bereaved a little extra comfort.

Tomobiki is supposed to be bad, bad news, because the word translates as 'pulling a friend'. It conjures the image of being pulled into death to go with your friend. If a funeral really must take place on that day, folklore tells of a doll placed in the coffin so that it, and not a friend, is dragged to the next life.

(100% codswallop, of course. If a supernatural entity could be powerful enough to pull somebody into death, it should also be able to differentiate between a doll and a human corpse.**)

* Britain and her colonies retained the Murder Act of 1752 until capital punishment was abolished in the 20th century. This Act specified that execution could not take place on a Sunday. The US has a similarly hypocritical custom of not scheduling executions between sundown Friday and sundown Sunday to avoid both the Jewish Shabbat and Christian Sabbath.

** On a more serious and personal note, this page's author has attended a Japanese funeral on a Tomobiki day and can confirm that the family did not consider Rokuyo at all; neither did any particular bad luck follow the event. No doll was placed in the coffin and the funeral proceeded with decorum. As with most deaths, no emotional capacity remained to consider superstitions.

Lucky Days for Sickness

As with birth delivery days, medical treatment tends to be too important to risk relying on superstition.

To trust an ancient custom with a dodgy reputation would be to say that Rokuyo had miraculous powers, and it is commonly accepted that miracles are the working of a divine power. If you feel that Rokuyo or astrology is divine, then you are missing out on something infinitely more wonderful.

Mankind has an inherent and healthy fear of sickness. No sane superstitious person* would consider agreeing to surgery on Butsumetsu.

Some people may also consider Rokuyo when being discharged from a hospital. The unlucky day Butsumetsu often precedes the lucky day Taian. Rather than risk discharge on an unlucky day, there is evidence** that some patients extend their stay by an extra 24 hours to be discharged on Taian. This may sound quaint, but a consequence is an increased cost of medical care in Japan. A relatively small increase of course, but given the billions spent on medical care, this extra astrologically inspired cost has astronomical consequences.

A similar phenomenon affects Western hospitals, with patients avoiding surgery on Friday the 13th.

* A sane superstitious person? Now there's an oxymoron!

** Influence of superstition on the date of hospital discharge and medical cost in Japan (BMJ. 1998 December 19; 317(7174): 1,680-1,683)

Doing Business in Japan

Should the days of Rokuyo concern the Western businessman negotiating with Japanese? Well, there is plenty of evidence that Japanese businessmen do consider superstitions when making decisions.

Look, for example, at the popular story of the largest Japanese car maker. The company started with the owner's name, Mr Toyoda, but gave the launch an extra bit of luck by naming the company Toyota. And that is luckier because to spell Toyota using katakana, you use eight pen strokes. (トヨタ) and eight is a lucky number. Silly? Maybe. But Toyota has been pretty successful over the years.

Do Japanese businessmen consider superstitious days? Can we examine how they behave and use this information to model our own behaviour and improve our chances?

Here are a few clues. For some Japanese companies:

  • commercial and domestic construction projects often start on Taian
  • new or refurbished branch offices delay opening until the next Taian
  • office moves are scheduled for Taian
  • product launches avoid Butsumetsu
  • electricity producers report to the Ministry of Economy and Industry every time they change their charging rates, always on Taian.

However these examples are about as far as it goes.

If you are about to do business with a Japanese company, don't fret about lunar calendars at the expense of improving the quality of the product or service you are trying to sell. Our overall recommendation is to not worry about Rokuyo. As with the popular discounts offered to couples to marry on Butsumetsu, business is about money, and the opportunity for profit tends to be a much more powerful influence than superstition.

And a note about national holidays in Japan: Despite the apparently large number of Japanese tourists, many Japanese workers traditionally don't take all their annual leave entitlement. So when the office closes for a National Holiday in Japan, those days are especially precious. Arrange a teleconference call on one of those days and see how quickly you lose favour with your Japanese customers.

丙午 Hinoe-Uma (the "Fire Horse") and the Baby Boom

The end of the baby boom could itself be the result of a superstition. Hinoe-Uma is a calendar event that occurs every 60 years.


Rokuyo Calendar Showing the Six Days

Other Sources

Other 'lucky' pages:


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