Time until the first day of spring

Astronomical spring in the northern hemisphere begins at the March equinox, when the sun crosses the celestial equator and day and night are close to equal. The exact instant shifts between 19 and 21 March from year to year, and it is a single moment worldwide rather than a local date. This countdown uses 20 March as an approximation. Meteorologists use a different convention entirely, starting spring on 1 March so that seasons line up with whole months.

The equinox is less useful as a gardening or planning date than it looks, because the last frost dates that actually matter vary by hundreds of miles and several weeks. Clock changes sit close to it: European countries move forward on the last Sunday in March and most of North America in the second week of that month, so the evenings lengthen in a step rather than smoothly. School terms in the northern hemisphere are built around Easter rather than the equinox, so the spring break moves independently of this date. South of the equator the same instant begins autumn, and Australia and New Zealand use the meteorological convention that starts a season on the first of the month. Day and night are not quite equal at the equinox itself, since refraction and the size of the sun's disc add several minutes of daylight.

Ireland puts spring in February, March and April, following the older quarter that opens at Imbolc on 1 February, so an Irish child and a British forecaster disagree by a month about which season they are standing in. The East Asian solar terms begin spring at lichun in early February, which is why the Chinese and Japanese new year is described as a spring festival while the ground is still frozen. Iran ties Nowruz to the crossing itself rather than to a calendar date, so the year turns at the exact instant. Three defensible answers, spread across about seven weeks.

The next one falls on Saturday, 20 March 2027, and this page counts down to the midnight that starts it in whatever time zone your browser reports.

The equinox is the moment the centre of the sun crosses the celestial equator, which is the projection of the earth's own equator onto the sky. It is an instant rather than a day, and it is the same instant everywhere, so it can carry two dates at once: a crossing at ten in the evening Universal Time on 20 March has already been the 21st in Tokyo for several hours. It is also the only time of year when the sun rises due east and sets due west from everywhere on earth, which is why surveyors once used it to check an alignment.

The name promises equal day and night and the day does not deliver it. Sunrise and sunset are timed to the upper edge of the sun rather than its centre, and the atmosphere refracts the disc into view slightly before it has really risen, which together add eight to ten minutes of daylight at middle latitudes. The day on which the two really are equal has a name of its own, the equilux, and it falls a few days before the March crossing in the northern hemisphere and a few days after the September one. Near the equator it never quite happens at all.