Spring Equinox (Chunfen, 春分) falls on 20 or 21 March at solar longitude 0°, when day and night are nearly equal and spring is divided in half.
Solar longitude
0°
Type
Principal term (zhongqi)
Season
Spring
Order
No. 4 of 24
Usual dates
Mar 20–21
Meaning and Astronomy
Chunfen (春分) occurs when the sun reaches ecliptic longitude 0°, the astronomical vernal equinox, usually on 20 or 21 March. The sun stands directly over the equator and day and night are roughly equal everywhere; afterwards days in the Northern Hemisphere grow longer than nights until the summer solstice. Chunfen is a zhongqi (中氣) or principal term, the midpoint of the second lunar month.
Fen means 'to divide', in two senses: day and night are divided equally, and the term falls halfway between the Start of Spring and the Start of Summer. Because of atmospheric refraction, daylight on the equinox is actually a few minutes longer than night. The equinox is also the zero point from which every solar term's longitude is measured.
The Three Pentads
First pentad: The swallows return (玄鳥至) - swallows arrive from the south and begin nesting under eaves.
Second pentad: Thunder raises its voice (雷乃發聲) - thunder becomes a regular feature of spring weather.
Third pentad: Lightning first appears (始電) - flashes of lightning accompany the rain.
Climate and Farming
By now southern China and the lower Yangtze are fully in spring, with peach and plum in bloom. The north warms quickly but still sees cold waves, and parts of the northeast may get snow. Taiwan has more spring rain and coastal fog; Hong Kong remains humid and misty.
This is one of the busiest farming periods. Winter wheat in the north is jointing and needs water and fertiliser; in the south early rice is sown in seedbeds, and tree planting and spring sowing begin across the country. A proverb says 'when wheat stands up at Chunfen, every moment is worth gold' (春分麥起身，一刻值千金).
Customs
Emperors once performed a sun sacrifice at the equinox; in the Ming and Qing dynasties it took place at the Altar of the Sun in Beijing, now Ritan Park, with a moon sacrifice at the autumn equinox. A popular modern pastime is standing an egg on end, often said to be easiest on the equinox - in fact, with patience it can be done on any day, so it is simply a seasonal game. In parts of Guangdong people make soup from a wild amaranth called spring greens (春菜), wishing for a 'cleansed' body, and some families stick plain glutinous rice balls on bamboo skewers at field edges to 'glue the sparrows' beaks' so birds spare the crops.
The equinox is also a traditional time for spring ancestral rites, and some clans visit graves around now; many Hakka families in Taiwan do their grave rites in this period. Japan observes Vernal Equinox Day as a public holiday, and the surrounding week, higan, is a time for visiting family graves and eating botamochi rice cakes.
Seasonal Food and Wellness
Since day and night are balanced, traditional thinking treats the equinox as a symbol of yin-yang balance and favours regular routines, moderate food that is neither too cooling nor too heating, and an even temper. Seasonal ingredients include Chinese toon shoots, shepherd's purse, bamboo shoots and spinach. These are general traditions, not medical advice.