The first day of Spring arrived today on Tuesday, March 20th, coming at the end of a winter that for the most part really wasn't for most of the U.S. and many countries around the world. In the U.S. it was the warmest winter in the 21st century and the 4th warmest winter since temperature record keeping began 117 years ago.

The first day of Spring is also known as the vernal or Spring equinox. This is the point in space and time when the sun moves across the celestial equator, an invisible circle projected into the sky above the Earth's equator. What this means for those in the Northern Hemisphere is that the days will grow longer and the nights shorter. In the Southern Hemisphere, the same equinox marks the beginning of longer nights and shorter days and is the beginning of autumn.

Springtime brings increasing daylight, warming temperatures, and the rebirth of flora and fauna. It is also the time when worms begin to emerge from the earth, ladybugs land on screen doors, green buds appear, birds chirp, and flowers begin to bloom. Love is in the air and people and animals seem to move with a spring in their step. Soon new babies will be born to many animal species in the world and baby birds will hatch. It is a wonderful time of renewal and a symbolism of hope for all on Earth.

What is an Equinox?

An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day have approximately equal length.

At an equinox, the Sun is at one of two opposite points on the celestial sphere where the celestial equator (i.e. declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: classically, the vernal point and the autumnal point. By extension, the term equinox may denote an equinoctial point.

An equinox happens each year at two specific moments in time (rather than two whole days), when there is a location (the subsolar point) on the Earth's equator, where the center of the Sun can be observed to be vertically overhead, occurring around 20 March and 22 September each year.

Although the word equinox is often understood to mean "equal [day and] night", this is not strictly true. For most locations on earth, there are two distinct identifiable days per year when the length of day and night are closest to being equal; those days are referred to as the "equiluxes" to distinguish them from the equinoxes. Equinoxes are points in time, but equiluxes are days. By convention, equiluxes are the days where sunrise and sunset are closest to being exactly 12 hours apart.
Source ~ Wikipedia