The question when’s the first day of spring has a deceptively simple feel—but the answer changes depending on whether you mean astronomical spring, meteorological spring, or the moment the Sun’s position defines an equinox.
When’s The First Day Of Spring in 2026, in Eastern Time (ET)?
Astronomical spring begins at the vernal (spring) equinox, the moment when the Earth reaches a point in its orbit where its tilt is neither toward the Sun nor away from it, and the Northern and Southern Hemispheres receive an equal amount of sunlight.
For 2026, the vernal equinox arrives on Friday, March 20, at 10: 46 a. m. EST. The equinox happens at the same moment worldwide. In the Northern Hemisphere, it marks the start of spring; south of the equator, where seasons are reversed, it marks the first day of autumn.
The equinox does not land on a fixed calendar date every year. It can fall between March 19 and March 21, depending on the year, reflecting the way Earth’s orbit and tilt interact over time.
If the equinox is about “equal night, ” why aren’t day and night exactly equal?
The term “equinox” comes from Latin roots meaning “equal” and “night, ” and the equinox is widely associated with the idea that day and night are the same length. In practice, they last almost the same amount of time—and in some places, the balance can be off by a few minutes.
One explanation is how daylight is measured around sunrise and sunset. At the equinox, the timing is taken from when the center of the Sun is at the horizon, producing a nominal 12-hour span between sunrise and sunset. But the Sun’s top edge becomes visible first at sunrise and remains visible last at sunset. Light refraction also keeps conditions bright for a short time even after the Sun is no longer visible, adding a little extra time to daylight hours.
Another complication is that the day when daylight and night are actually equal can occur on a different date than the equinox. In the UK, that equal-daylight point is called the equilux, and it arrives a few days before the spring equinox. In spring, this means the date when day and night are truly equal happens before the equinox.
The hidden contradiction: spring for astronomers, spring for forecasters
Part of the public confusion around when’s the first day of spring comes from the fact that “spring” can start on different dates depending on which definition is being used.
For weather forecasters, spring begins on March 1. That definition groups spring into the months of March, April, and May, a choice designed to make weather observations easier to compare year-on-year.
Astronomical spring, by contrast, begins at the spring equinox, and that moment can shift slightly each year. This split can create a contradiction in everyday life: forecasts may talk about “spring” weeks before the equinox, while the astronomical start arrives later and at a precise time of day.
After the vernal equinox, days grow longer every day in the Northern Hemisphere—while in the Southern Hemisphere they grow shorter—until the June solstice. Solstices are the points when Earth’s tilt is tipped most extremely either toward or away from the Sun, making day and night most unequal.
So, if you are asking when’s the first day of spring in the strict astronomical sense, the answer is the equinox moment itself—Friday, March 20, 2026 at 10: 46 a. m. EST. If you mean the seasonal framework used by forecasters for consistent record-keeping, spring starts March 1.
