Solar month

Meaning

A solar month runs from one of the twelve terms that open months to the next: about thirty days, in which the Sun moves thirty degrees along its path. It is the month of the Chinese solar calendar, the one the four pillars, the Flying Stars and the month animal are counted by: the Tiger month from Lichun, the start of spring, about 4 February, the Rabbit month from Jingzhe, about 6 March, and so round to the Ox month from Xiaohan, about 6 January, which closes the year.

The twenty-four solar terms take turns: twelve open the months, the jie, and twelve fall in their middle, the principal terms. Lichun opens the Tiger month and Yushui marks its middle; the solstices and the equinoxes are all principal terms, so the winter solstice falls in the middle of the Rat month and the spring equinox in the middle of the Rabbit month. Each solar month is named by its branch and its animal, and in BaZi its pillar follows from the year’s.

It is not the month of the Chinese New Year. The calendar people celebrate by is lunisolar: its months run from new moon to new moon, twenty-nine or thirty days, and a leap month comes seven times in nineteen years. The two counts live side by side, and almanacs print both; the traditions that read time by the Sun, BaZi and Feng Shui above all, count by the solar month.

In practice

• In BaZi the month pillar is the solar month’s, and the month branch decides which phase is in season, and so how strong every other one is; the luck pillars are timed by the days between the birth and the next, or the last, opening term.
• In Chinese astrology the month animal is the solar month’s animal, and the Cycles lens reads the twelve months of the year ahead, each from its opening term, by how they meet the reader’s animals.
• In Feng Shui the monthly stars change at each opening term, the 5 Yellow among them, and the month’s star in the centre is read with the year’s.
• Near a change: a birth within five minutes of an opening term is marked as uncertain, since a slightly different birth time could give the month before or after.

Across traditions

• In Western astrology the Sun’s entry into a sign opens a month of the same kind, thirty degrees of the Sun, but the two are offset by half a sign: the Tiger month begins with the Sun at 15° Aquarius, the Rabbit month at 15° Pisces.
• In India solar months that open as the Sun enters a sign of the sidereal zodiac, at each sankranti, set the year in Tamil Nadu, Kerala and Bengal, while lunar months rule elsewhere: the same choice between the Sun and the Moon, made differently from region to region.
• The Celtic year has its festivals near the Chinese starts of the seasons: Imbolc close to Lichun, Beltane to Lixia, Lughnasadh to Liqiu and Samhain to Lidong, each halfway between a solstice and an equinox.

Origin and history

Months that follow the Sun are as old as the twenty-four terms, which the Huainanzi lists complete in 139 BC. The calendar kept them beside the Moon’s months: since the Taichu calendar of 104 BC, a lunar month with no principal term has been the leap month, the rule that ties the Moon’s months to the Sun’s year, and since the Shixian calendar of 1645 the terms have followed the Sun’s true motion rather than an average.

The schools that read births made the solar month their own. The Yuanhai Ziping and the San Ming Tong Hui count a birth’s month from the term that opens it, so a child born the day before Jingzhe belongs to the Tiger month whatever the lunar calendar says, and Shen Xiaozhan’s Ziping Zhenquan made the month branch the key to every chart. The almanacs, and the Feng Shui manuals after them, changed their monthly spirits and stars at the same terms.

How Ulune calculates it

Ulune finds the solar month between the two opening terms around an instant, from a table of the solar terms computed with the Swiss Ephemeris for 1800 to 2200, which the device reads. Months are counted from the Tiger month, the Ox month closing the year that Lichun opened. The month pillar counts from Bing-Yin, the Tiger month of 1984, as an unbroken run of months through the sixty-cycle, which gives the same stems as the rule of the five tigers. A month changes at an instant of the Sun’s motion, so no clock or time zone moves it.

Correspondences