You can obtain the dates of the seasons (equinoxes and solstices) and apsides (perihelion and aphelion) of the orbit of the Earth by typing the year (1700-2100) in the space below and clicking on the "Find dates" button.
The calculator provides the computed times of the beginning of the seasons as well as Earth's perihelion and aphelion. The times of the equinoxes mark the beginning of spring and fall. The times of the solstices mark the beginning of summer and winter. Definitions of these terms can be found in The Astronomical Almanac Online glossary.
Variation in Times of Perihelion and Aphelion explains why the times of these events appear to vary more than those of the others while The Seasons and the Earth's Orbit discusses how all of these phenomena relate.
For U.S. time zones (Form A), phenomena times are presented in the standard time or daylight time (see below) requested. Standardized time zones were introduced in the U.S. in 1883.
In accordance with the Uniform Time Act of 1966 and subsequent legislation, daylight time (DST) can be implemented only for U.S. time zones (Form A) from 1967 to the present day.
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