Japan / Calendars
Rokuyo Calendar: 六曜 and Japanese Old-Calendar Dates
Look up rokuyo for dates from 1901 to 2099. View a month with Japanese old-calendar month and day, readings for all six names, and a printable month.
Rokuyo Calendar: 六曜 and Japanese Old-Calendar Dates: Uses astronomy-engine to find new moons and principal solar terms, then assigns Japanese old-calendar months on JST civil days. Seasonal anchors resolve ordinary leap-month candidates. For the 2033 conflict it follows the calendar association's recommended leap 11th month, starting 22 December 2033. Rokuyo are a calendar custom, not predictions or advice. Runs 100% locally in your browser with zero server file uploads.
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Choose any date from 1901 to 2099. Days begin at midnight in Japan (UTC+9).
先勝
せんしょう/さきがち
Old-calendar year 2026
The name means ‘preceding victory’ in the traditional six-day cycle.
2026-10 · 六曜 / 旧暦
Rokuyo are a calendar custom, not a prediction of events or advice about what to do.
| Sun | Mon | Tue | Wed | Thu | Fri | Sat |
|---|---|---|---|---|---|---|
- 先勝 (せんしょう/さきがち)
- The name means ‘preceding victory’ in the traditional six-day cycle.
- 友引 (ともびき)
- The name is written with characters meaning ‘friend’ and ‘pull’.
- 先負 (せんぶ/さきまけ)
- The name means ‘preceding defeat’ in the traditional six-day cycle.
- 仏滅 (ぶつめつ)
- The name is written with characters meaning ‘Buddha’ and ‘extinction’.
- 大安 (たいあん)
- The name means ‘great peace’ in the traditional six-day cycle.
- 赤口 (しゃっこう/しゃっく)
- The name means ‘red mouth’ and is one of the six traditional calendar labels.
2033–2034 follows the calendar association's 閏11月 recommendation: the leap month begins on 22 December 2033. Modern old-calendar dates are a convention, not an official Japanese civil calendar.
NAOJ: old-calendar rulesCalendar association: 2033 recommendation
Astronomical days and month numbering
NAOJ explains modern old-calendar construction using new moons, principal solar terms and the four equinox/solstice month anchors. The 1984–1985 and 2014 examples are regression fixtures. Source: https://eco.mtk.nao.ac.jp/koyomi/topics/html/topics2014.html
2033 recommendation and rokuyo
The Japan Association for Calendars and Culture Promotion recommended leap month 11 on 28 August 2015. Its presentation includes the month-start alternatives and rokuyo examples. The autumn equinox month-8 constraint must be relaxed in 2033 to preserve winter solstice in month 11. Source: https://www.rekibunkyo.or.jp/files/img/top/20150828_2033mondaikenkai00.pdf
Dates far in the future rest on predicted Earth rotation (ΔT), so a new moon within about a minute of midnight JST can move a month start by one day. The new moon of 22–23 August 2074 is such a case; this tool starts that month on 22 August, and official tables may differ once published.
JST new-moon check
NAOJ's 2027 astronomical calendar places the February new moon on 7 February at 00:56 JST. The date differs from UTC+8 calendars. Source: https://eco.mtk.nao.ac.jp/koyomi/yoko/2027/rekiyou273.html
How to use it
- Choose a Gregorian date, interpreted in Japan Standard Time (UTC+9).
- Read the rokuyo, its reading and the old-calendar date; browse adjacent months or select a day in the grid.
- Print the displayed month, or copy the selected date.
Privacy & limitations
Date calculations and printing run in your browser. Your selected date is not uploaded.
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Frequently asked questions
How is rokuyo calculated?
Add the old-calendar month number and day number, then take the remainder after division by six: 0 大安, 1 赤口, 2 先勝, 3 友引, 4 先負, 5 仏滅. A leap month uses the previous month's base number.
Why can a date differ from a Chinese lunar calendar?
This calendar uses Japan Standard Time (UTC+9), not UTC+8. The Japanese old-calendar new year in 2027 is 7 February: NAOJ lists the new moon at 00:56 JST that day.
What happens in 2033?
The original seasonal constraints conflict. The Japan Association for Calendars and Culture Promotion recommends leap month 11. This tool uses that convention: 22 December 2033 is leap 11/1 and 19 February 2034 is 1/1. NAOJ does not issue an official modern old calendar.
What should I select when printing?
Use A4 landscape and turn off browser headers and footers. The print action includes only the displayed calendar, readings and explanatory notes.
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