Rokuyo, Japan's Six-Day Calendar Cycle: What Taian and Butsumetsu Mean, Their Order, and Choosing Dates

The six rokuyo and what they mean

Rokuyo is a calendar annotation made up of six days: Senshou, Tomobiki, Senbu, Butsumetsu, Taian and Shakkou. A distinctive feature is that luck is said to vary by time of day, not just by day. Few people go that far when choosing, but knowing the background makes the meaning of the order easier to understand.

There are several readings: some regions read 先勝 as "senkachi" and 赤口 as "sekiguchi". Since it's a form of fortune-telling, the explanations of meaning also vary slightly between calendars and books. It's fair to say there's no strictly correct answer.

The order is set mechanically by the old calendar

Rokuyo aren't decided by fortune-tellers; they're calculated from dates in the old lunisolar calendar. They advance one per day in the order Senshou → Tomobiki → Senbu → Butsumetsu → Taian → Shakkou, and reset when the lunar month changes.

As a formula, it's determined by the remainder when (lunar month + lunar day) is divided by 6. A remainder of 0 is Taian, 1 Shakkou, 2 Senshou, 3 Tomobiki, 4 Senbu and 5 Butsumetsu. For lunar 1/1, 1 + 1 = 2, so Senshou; for lunar 5/1, 5 + 1 = 6, which leaves a remainder of 0 when divided by 6, so Taian.

• On today's (Gregorian) calendar, rokuyo look like a regular 6-day cycle.
• But on the day the lunar month changes, the order jumps, and a Taian can be followed by another Taian.
• The lunar month changes on the day of the new moon, which shifts each year in the Gregorian calendar. So "this year's Taian days" don't fall on the same dates as last year's.
• They're not linked to the days of the week either. Weekends aren't always Taian.

The jumps are evidence that rokuyo are tied to the old lunar calendar. To sort out the relationship between the old and new calendars and between Japanese era and Western years, see Converting Japanese Era and Western Years.

How long have they been used?

Rokuyo is a calendar annotation of Chinese origin, thought to have reached Japan around the Kamakura to Muromachi periods. It only became widely printed in ordinary people's calendars in the late Edo period, and settled into its current form relatively recently.

• In the Meiji calendar reform, it was removed from calendars as a baseless annotation of luck.
• It continued to appear in private calendars nonetheless and spread again after the war.
• Even today, some local governments have a policy of not printing rokuyo on their official calendars.
• The names have also changed over time; Tomobiki was originally 共引, meaning a day when contests end in a draw.

In other words, it's not as ancient as "long-standing tradition" suggests, and its meanings have been reinterpreted along the way. The association of Tomobiki with "pulling a friend along" is said to be an interpretation that arose after the character 共 was changed to 友 (friend). Many customs around age and years have followed a similar path; reading Yakudoshi Age Chart and How to Find Your Eto and Star Sign together will give you the background.

How much to take them into account for weddings and funerals

In practice, weddings and funerals are affected most. Funeral scheduling in particular can be constrained by facilities for rokuyo reasons, so you need to know about it whether or not you care.

Tomobiki funerals are avoided because the word sounds like "pulling a friend along" (into death), not because of Buddhist teaching. But in some regions crematoriums close on Tomobiki, and then you simply can't schedule it. Since that's a matter of facilities rather than custom, the realistic approach is to check the local crematorium's opening days first.

How to look up the rokuyo

Many Japanese daily calendars and planners print the rokuyo. If you don't have one to hand, or want to check a date further ahead, the following steps are reliable.

1. 1

   Find the lunar date for that day

   Rokuyo are determined by the lunar month and day, so first convert the Gregorian date to the lunar calendar, using a calendar that shows lunar dates or almanac data.

2. 2

   Add the month and day

   Add the lunar month and day. For lunar 8/15, for example, 8 + 15 = 23.

3. 3

   Look at the remainder after dividing by 6

   23 ÷ 6 = 3 remainder 5. A remainder of 5 is Butsumetsu. Remainders map as 0 Taian, 1 Shakkou, 2 Senshou, 3 Tomobiki, 4 Senbu, 5 Butsumetsu.

4. 4

   Check against the days around it

   Work out the days before and after too, and see whether they run Senshou → Tomobiki → Senbu → Butsumetsu → Taian → Shakkou. If the order jumps, that's where the lunar month changes.

You can also check rokuyo month by month in the Lucky Day Calendar; tap a date to see its lunar date and other selected days that fall on the same day, such as Ichiryumanbai-bi, Tenshanichi and Fujojuu-bi. Lucky and unlucky days from systems other than rokuyo are covered in What Is Ichiryumanbai-bi?, What Is Tenshanichi? and What Are Fujojuu-bi and Sanrinbo?, and choosing a date to register a marriage in How to Choose a Marriage Registration Date. How to count the days until a milestone is in How to Count Days to an Anniversary, and the rules for writing dates on vertical invitations and certificates in How to Write Dates Vertically.

FAQ

How is the order of rokuyo decided?

It's calculated from the lunar date. They advance one per day in the order Senshou, Tomobiki, Senbu, Butsumetsu, Taian, Shakkou, and reset on the 1st of each lunar month. The 1st of lunar months 1 and 7 is Senshou, months 2 and 8 Tomobiki, and so on: each month has a fixed starting point. As a formula, it's the remainder of (lunar month + lunar day) divided by 6, with 0 Taian, 1 Shakkou, 2 Senshou, 3 Tomobiki, 4 Senbu and 5 Butsumetsu. When the order suddenly jumps on a Gregorian calendar, that's where the lunar month changes.

Is it wrong to hold a wedding on Butsumetsu?

There's no rule. Rokuyo is a calendar annotation of Chinese origin with no direct connection to Buddhism or Shinto, and the 仏 (Buddha) in Butsumetsu is said to have originally been 物 (thing). In fact, Butsumetsu and Shakkou are easier to book, and some venues offer discounts. The thing to watch for is that relatives may care strongly even if the couple don't. Checking with everyone before fixing the date avoids having to rearrange later after someone objects.

Why are funerals said to be avoided on Tomobiki?

Because the word sounds like "pulling a friend along", it became associated with the deceased taking a friend with them; it doesn't come from Buddhist teaching. It was originally written 共引, meaning a day when contests end in a draw. But as the custom took hold, some crematoriums in some regions came to close on Tomobiki, in which case a farewell ceremony is physically impossible. Wakes are generally held even on Tomobiki. Check the local crematorium's opening days before setting the schedule.

How often does Taian come round?

The six rokuyo cycle in order, so on average Taian comes once every 6 days, about 5 times a month. But the order resets when the lunar month changes, so the count varies by month and Taian can even fall on consecutive days. Taian days that coincide with weekends are limited each year, and wedding and car-delivery bookings concentrate on them, so they fill up unless you book early. Insisting on a Sunday Taian narrows your options sharply, so it's easier to come up with several candidate dates before consulting venues or companies.