Rokuyo & Lunar Calendar (Japanese Lucky Days)
Pick a year and month to see a calendar with each day’s rokuyo (the six-day Japanese luck cycle: Taian, Tomobiki, Sensho, Senbu, Butsumetsu, Shakko) and the old Japanese lunar date. It also marks the 24 solar terms and Japanese national holidays, so you can pick out the lucky Taian days for a wedding, a move or a car delivery. The lunar dates are calculated from the new moon and the sun’s position, and nothing you enter is sent to a server. For a printable calendar with week numbers, try the Calendar Generator.
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Look up a date
How to use
- Set the “Year” and “Month” to show that month with rokuyo and lunar dates.
- Choose a rokuyo such as Taian under “Highlight rokuyo” to colour those days.
- To check a single day, enter it under “Look up a date”.
Notes
- Lunar dates are computed astronomically from the new moon and the sun’s ecliptic longitude, for 1900–2100. The calculation has an error of a few minutes, so when a new moon or solar term falls within about ten minutes of midnight, the result can differ by one day from the almanac published by the National Astronomical Observatory of Japan (for example, the 2023 summer solstice at about 23:58 JST on June 21 shows as June 22). For important dates, double-check against an official almanac.
- Rokuyo is a folk custom with no scientific basis and guarantees nothing. How much weight it carries at weddings, funerals and other events varies by region and family.
- The placement of the 2033 leap month is famously disputed. This tool follows the rule “the month containing the winter solstice is month 11; if 13 months pass before the next solstice, the first month without a major solar term is the leap month”, which gives a leap month 11 in 2033.
- Holidays are shown for 2000–2099 only, and later legal changes or one-off holidays are not reflected.
Glossary
Rokuyo
A six-day cycle (Taian, Tomobiki, Sensho, Senbu, Butsumetsu, Shakko) used in Japan to mark the luck of a day. It is the remainder of (lunar month + lunar day) divided by 6, counted as Taian, Shakko, Sensho, Tomobiki, Senbu, Butsumetsu. The count restarts every lunar month, so it looks irregular on the Gregorian calendar.
Lunar calendar (lunisolar)
A calendar whose months run from one new moon to the next, with leap months inserted to keep it in step with the seasons. Japan used it until 1872. Today “the old calendar” usually means the Tenpō-era rules applied with modern astronomical calculation.
Leap month
An extra 13th month added to keep the lunar calendar aligned with the seasons. A month that contains no major solar term becomes the leap month and is named after the previous month with “leap” added.
24 solar terms
The year divided into 24 seasonal markers by the sun’s ecliptic longitude, such as Start of Spring, the equinoxes and the solstices. Terms every 15° exist; the “major” ones every 30° decide lunar month names and leap months.
FAQ
How is the rokuyo for a day decided?
Add the lunar month and lunar day, divide by 6, and read the remainder: 0 is Taian, 1 Shakko, 2 Sensho, 3 Tomobiki, 4 Senbu, 5 Butsumetsu. Lunar 1/1 gives 1 + 1 = 2, so it is always Sensho. Because the cycle restarts every lunar month, it looks irregular on the Gregorian calendar.
Do the lunar dates always match the official Japanese almanac?
Almost always, but this is not guaranteed. The tool calculates new moons and the sun’s ecliptic longitude astronomically, so when a new moon or solar term falls very close to midnight in Japan Standard Time, the result can be off by one day, because the calculation has an error of a few minutes. For important dates, check an official almanac such as the one from the National Astronomical Observatory of Japan.
What is the rokuyo of a leap-month day?
A leap month is counted with the same number as the month before it. For example, leap month 6, day 1 in 2025 (July 25) is 6 + 1 = 7, remainder 1, so Shakko. The calendar marks it as “L6/1”.
Should I avoid Butsumetsu or Tomobiki for weddings and funerals?
Rokuyo has no legal or scientific force; whether to follow it is up to you and your family. Taian and Tomobiki are popular for weddings and Butsumetsu is often avoided (venues may discount it). For funerals, many crematoria in Japan close on Tomobiki days, so check availability first.
Which years are supported?
1900 to 2100. Only the holiday display is limited to 2000–2099; outside that range you still get rokuyo and lunar dates without holidays. The 2033 leap month is disputed, and this tool follows the winter-solstice rule, which makes it leap month 11.
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