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Posted by Kinakinw | --:-- | Comment [0] | TrackBack [0] | スポンサー広告

02 2010

System of twenty-four Seasonal Divides

I wrote in the last post that “shochuu-mimai (暑中見舞い)” is sent from the end of the rainy season until the beginning of fall (立秋, ritsushu) according to the calendar. Ritsushu is Aug. 7 or 8, and after that day, the greeting card is called “zansho-mimai (残暑見舞い).” Zansho means late-summer heat.

This custom is common knowledge even Kinakinw knows.

So, what calendar does ritsushu belong to?
I vaguely assumed it would be based on the lunar calendar (旧暦) for a long time. But, it was not accurate, to say the least.

Ritsushu that divides shochuu-mimai between zansho-mimai is one of “twenty-four setsuki (二十四節気)”, a system of twenty-four seasonal divides of the solar year. It was originated in ancient China to make date on the lunar calendar correspond to seasons based on the solar calendar.


According to the lunar calendar, each month started on the day of new moon. The period between new moon and the next was 29.5 days on an average, and then there were about 354 (multiply 29.5 by 12) days in a year, which was 11 days shorter than 365 days year on the solar calendar. Thus, the difference between the calendar date and seasons was getting large year after year. When the difference was reaching 29.5 days, an intercalary month (閏月: uruu-tsuki) was added. (That year had 13 months.) Twenty-four setsuki was the criterion for deciding when an intercalary month was added. (HP of National Astronomical Observatory of Japan: NAOJ)

As already mentioned in the previous post, “Cherry Blossoms and Saigyo”, a specific date in the lunar calendar varies on the basis of 365 days year. To know the seasons was really important for agricultural work.


In twenty-four setsuki, a solar year is firstly divided into four seasons, and secondly, each season is divided into six priods. Japanese still know many of them as words that express seasons.

2010’s Setsuki in August
“Ritsushu (立秋, the beginning of fall)”: August 7
“Shosho (処暑, the end of summer heat)”:August 23

The calendar was reformed in 1872. Though the lunar calendar is no longer official, even now NAOJ announces the date of each setsuki every year.


Posted by Kinakinw | 23:43 | Comment [0] | TrackBack [0] | Cultural Issue (Japan)

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