The first day of spring, commonly known as the spring equinox, occurs this year on March 20, 2011.
The spring equinox officially occurs at 23:31 UTC.
The equinox occurs twice each year, when the center of the sun is in the same place as the axis of the earth. On this day, the length of day and night are roughly the same – 12 hours each.
In the northern hemisphere, the spring equinox marks the traditional passage of seasons from winter to spring.
The spring equinox is also known as the vernal equinox, from the Latin for “spring” and “equal night.”
There are many cultural traditions associated with the first day of spring, including the religious celebration of Ostara. Christian churches typically celebrate Easter on the first Sunday after the first full moon, on or after the first day of spring. Easter Sunday occurs this year on April 24, 2011.
The first day of spring 2011 falls one day after the full moon on March 19, 2011.
The Greek mathematician and astronomer Hipparchus is widely thought to have discovered the equinoxes.
The fall equinox (a.k.a. autumnal equinox) takes place on September 23, 2011, at 9:04 UTC.