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Bodhastra
Your birth date

Date-only systems resolve immediately. Systems that require a birth time or place will say so instead of guessing.

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Eto and junishi in Japan: native readings, regional animals and a civil calendar remade in 1873.

Facts & lineage · civil boundary

January 1 is modern, not timeless

Japan’s current year-animal boundary is easy to calculate. The difficult part is stating where that rule begins.

The cut in the calendar

The Meiji government announced the change in the eleventh month of 1872. Under the decree, the old calendar’s Meiji 5, month 12, day 3 became 1 January 1873. The official year then followed the Gregorian solar calendar.

This is why a modern date anywhere between 1 January and 31 December carries the same year eto. It is also why the Chinese lunar-new-year rule must not be reused on the Japanese calculator.

Two date contracts

datecalendar contractcalculator
1873 onwardGregorian civil year adopted by Japansupported; changes 1 January
before 1873historical Japanese lunisolar calendar then in forcenot backfilled; needs conversion

What a future historical calculator needs

It must accept a named Japanese era and lunisolar month, distinguish leap months, identify which official calendar governed the date, and only then convert it. A proleptic Gregorian year field would look simpler while answering a different question.

Bodhastra documents what astrological traditions have said, and when they started saying it. It is presented as cultural history and entertainment. Nothing here is medical, psychological, financial or predictive advice, and nothing here is a claim about what will happen to you.

Every source, listed

Place data from GeoNames, used under CC BY 4.0.