Equinox

First Day Of Spring 2023: Vernal Equinox

This (not to scale) image shows how our planet receives equal amounts of sunlight during equinoxes. Credit: NASA/GSFC/Genna Duberstein

The Vernal Equinox, marking the changing of the astronomical Seasons from the last day of Winter to the first day of Spring, occurs on March 20th at 5:24 p.m. Eastern Standard Time.

Equinox means “equal night” in Latin, capturing the idea that daytime and nighttime are equal lengths everywhere on the planet. That is true of the Sun’s presence above the horizon, though it does not account for twilight when the Sun’s rays extend from beyond the horizon to illuminate our gas-filled atmosphere.

It is an equal amount of day and night in the northern hemisphere for locations like Melbourne, Florida, but also in the southern hemisphere for locations like Melbourne, Australia.

The apparent change in the location of the sun and moon marks important dates for hunting, fishing, and farming.

Of course, it is not the Sun that is moving north or south through the seasons, but a change in the orientation and angles between the Earth and its nearest star.

The axis of the Earth has tilted 23.5 degrees relative to the Sun and the ecliptic plane. The axis is tilted away from the Sun at the December solstice and toward the Sun at the June solstice, spreading more and less light on each hemisphere.

At the equinoxes, the tilt is at a right angle to the Sun, and the light is spread evenly.

Scenes of Earth from orbit from season to season, as viewed by EUMETSAT. Notice how the terminator – the line between day and night – touches both the North and South Poles in the equinox images. See how the shadow is lopsided for each solstice, too: sunlight pours over the Northern Hemisphere for the June solstice, while the sunlight dramatically favors the Southern Hemisphere for the December solstice.
Images: NASA/Robert Simmon

As pictured in this NASA Earth Observatory photo, the Spring Equinox is caused by the tilt of the earth’s rotating axis.

How can it be Spring if it is still snowing in parts of the United States?

Blame the oceans, which heat up and cool down only slowly. By March 20 they are still cool from the winter time, and that delays the peak heat by about a month and a half. Similarly, on the first day of Fall in September, the ocean water still holds warmth from the Summer, and the hottest days are still, on average, a month and a half ahead.

When Do We Turn Our Clocks Forward In 2023?

Naturally, many people think that with the changing of the seasons comes the changing of their clocks at the beginning of Spring 2023. But this is not the case.

It is true, however, that a helpful way to remember whether to set our clocks ahead or behind one hour during daylight savings time is to “Fall Back” and “Spring Ahead.”

Daylight Savings Time (DST) will begin for Florida at 2 a.m. on Sunday, March 12, 2023.