Toji (The Winter Solstice) (冬至)
Toji (the winter solstice) is one of Nijushi-sekki (the 24 divisions of the solar year). It occurs around December 22 at ecliptic longitude 270 degrees. And it refers to a period between the day and the beginning of the following sekki called shokan (the lesser cold season) (at ecliptic longitude 270 - 285 degrees).
It is the shortest day and longest night of the year, with the lowest culmination altitude of the sun, in the northern hemisphere.
(It is actually a few days out, however. See the "Daytime (astronomy)" article for details.)
"Koyomi Binran" (the Handbook of Japanese Calendar) explains 'it is because the sun reaches the most southern point and the daytime is the shortest.'
It is said in Japan that taking yuzu-yu (a yuzu citron bath) and eating Toji-gayu (winter solstice rice gruel), which is azuki-gayu (rice gruel with red beans), and pumpkins on the day prevent catching cold. There is a tradition of eating jiao-zi (Chinese dumplings containing ground meat and/or vegetables) in Northern China and tan-en (boiled dango (dumplings) with an (sweet bean paste) inside) in Southern China.
The sun rises from the slightly southerly direction from the due east and sets in the slightly southerly direction from the due west in the northern hemisphere during the period between the autumnal and vernal equinoxes. This heavenly body rises from and sets in the most southerly directions on the day of Toji. An observer on the Tropic of Capricorn would see the sun pass through the zenith at noon on the day of Toji. The polar night occurs in the whole Arctic Circle to the north of the northern latitude of 66.6 degrees, and the night of the midnight sun in the entire Antarctic Circle to the south of the southern latitude of 66.6 degrees, on the day of Toji.
Incidentally, the latest sunrise or earliest sunset of the year is not experienced on the day of Toji. In Japan, the latest sunrise occurs about half a month after Toji, and the earliest sunset about half a month before it.
Apart from the astronomical Toji, however, 'the day with the shortest daytime and longest nighttime' is also called Toji sometimes by tradition. The relationship between the lengths of daytime and nighttime is reversed in the southern hemisphere. Thus, the day of Toji in a traditional sense in the southern hemisphere is actually Geshi (the summer solstice) in the original, astronomical sense.
Sakutan Toji (Toji that falls on November 1 in old lunar calendar and occurs every 19 years)
In ancient times, Toji marked the beginning of a year. As a result, even now, it is used as the basis for a calendar. According to the lunisolar calendar that was being adopted in China and Japan, November (in old lunar calendar) is defined as the month of Toji. Every 19 years the day of Toji falls on November 1 (in old lunar calendar). And this is called Sakutan Toji. In the lunisolar calendar, a cycle of 7 leap months in 19 years was called 'Sho' (a chapter) and the year, in which an old chapter was replaced by a new one, was named 'Shoshu,' meaning the first year of the new chapter. In the year of Shoshu, the seventh leap month concluded the preceding chapter, and the Toji following it marked the beginning of a new chapter. A general rule was to develop rekiho (a calendar-making method) in such a way that Toji is always Sakutan Toji in Shoshu.
Sakutan Toji comes around in an exact 19-year cycle. This indicates the correct application of the calendar based on the principle of 7 leap months in 19 years. The accuracy of the calendar was used as a proof of the proper administration of politics. And Sakutan Toji was splendidly celebrated. In China, this had been the practice since ancient times. And kentoshi (a Japanese envoy to Tang Dynasty in China) was allowed to attend the ceremony in 659 when it was staying by coincidence in the capital of Tang Dynasty, Rakuyo. In Japan, such a ceremony was held for the first time in 784 by the Emperor Kanmu, who had been actively adopting Chinese-style ceremonies. It became a very big event, since Goryaku no so (an annual ceremony, in which a calendar for the next year was submitted to an emperor) had also been originally held on November 1.
The calendar using a chapter-breaking method, however, did not always respect the rule of 7 leap months in 19 years. When it was not, the beginning of a new chapter did not necessarily coincide with the arrival of Sakutan Toji. On the contrary, there were circumstances in which Sakutan Toji accidentally occurred in the middle of a chapter. (This type of Sakutan Toji was called Rinji Sakutan Toji [casual Sakutan Toji]). In Japan, it was considered deplorable to neglect these conditions. And Sakutan Toji was brought on or avoided by the artificial manipulation of the calendar (which is a practice called 'kaireki' [calendar revision]). But, later Sakutan Toji that did not occur at the beginning of a chapter also came to be celebrated. The last ceremony of Sakutan Toji was held in 1768 at the time of the Emperor Kokaku. When the next Sakutan Toji arrived in 1870, the Meiji Government decided against organizing such a ceremony in the future, regarding it as an old convention.
The last Sakutan Toji took place in 1995, and the next one will occur in 2014.
The following is an easy mathematical way of determining the day of Toji between 1900 and 2099.
When the remainder after the division of the Christian Era by 4 is 0, Toji falls on:
December 22 between 1900 and 1988
December 21 between 1992 and 2096
When the remainder after the division of the Christian Era by 4 is 1, it falls on:
December 22 between 1901 and 2025
December 21 between 2029 and 2097
When the remainder after the division of the Christian Era by 4 is 2, it falls on:
December 23 between 1902 and 1918
December 22 between 1922 and 2058
December 21 between 2062 and 2098
When the remainder after the division of the Christian Era by 4 is 3, it falls on:
December 23 between 1903 and 1955
December 22 between 1959 and 2095
December 21 in 2099
Shichijuni-ko (the 72 divisions of the solar year)
The following are the divisions of Shichijuni-ko that fall into the Toji period.
Shoko (the first division)
Prunellae spica sprouts (in Japan).
Earthworms form clods under the soil (in China).
Jiko (the next division)
Elks shed their antlers (in Japan).
Sawashika no tsuno oru
Elks shed their antlers (in China).
Makko (the last division)
Yukiwarite mugi nobiru
Wheat sprouts under the snow (in Japan).
Frozen springs begin to stir under the ground (in China).
Preceding and following sekki
Toji is after the Taisetsu (the heavy snow season) and followed by Shokan.