Spring (Vernal) Equinox Countdown

The spring or vernal equinox, around March 20, is the moment the Sun crosses the celestial equator heading north, bringing nearly equal day and night everywhere on Earth and marking the astronomical start of spring in the Northern Hemisphere — while the Southern Hemisphere begins autumn at the very same instant.

History

Humans have watched for the March equinox since prehistory, and some of the world's most remarkable monuments were built to catch it. At Chichén Itzá in Mexico, the Maya engineered the El Castillo pyramid so that the equinox sun casts a serpent of light and shadow slithering down its staircase. The Mnajdra temples of Malta, raised more than five thousand years ago, frame the equinox sunrise through their main doorway, and at Angkor Wat in Cambodia the sun climbs directly over the central tower on equinox morning. These alignments show that early farming societies treated the equinox as a fixed anchor in the turning year. Calendars soon organised themselves around it. Nowruz, the Persian New Year with roots reaching back some three thousand years, still begins at the precise astronomical moment of the equinox and is celebrated by hundreds of millions of people. In China, Chunfen — 'spring's division' — is one of the twenty-four solar terms that have guided farming for over two millennia. The Christian church, at the Council of Nicaea in AD 325, tied the date of Easter to the first full moon after the March equinox, a rule still in use today. In Japan, older imperial rites of the season evolved into Shunbun no Hi, Vernal Equinox Day, established as a national holiday in 1948. Modern astronomy defines the equinox as the instant the Sun's centre crosses the celestial equator moving northward. Because the calendar year and the tropical year do not match exactly, that instant drifts between March 19 and 21 depending on the year and time zone. In 2010 the United Nations recognised March 21 as the International Day of Nowruz, and crowds still gather each year at Stonehenge, Teotihuacán and Chichén Itzá to greet the equinox sun exactly as their ancestors did.

Meaning

The equinox is one of only two moments in the year when day and night stand in near-perfect balance across the whole planet, and cultures everywhere have read that balance as a symbol of renewal, fairness and fresh starts. In the Northern Hemisphere it opens astronomical spring — the season of planting, blossom and lengthening light — which is why festivals of new beginnings, from Nowruz ('new day') to Easter's springtime calendar rule, cluster around it. In Japan it is a day for visiting family graves and reflecting on nature during the week of Higan. It is also a genuinely shared planetary event: the equinox happens at one single instant for everyone on Earth. And it is a reminder that the hemispheres mirror each other — the same moment that begins spring in New York or Tokyo begins autumn in São Paulo and Sydney.