It is the first full day of the astrological sign of Aries and thus marks the beginning of the tropical Zodiac.
International Astrology Day is celebrated/observed depending on the exact day that the Northward equinox actually occurs.
The date of the holiday occurs at the same time of the Iranian new year (Norouz), which is celebrated in many places throughout the Middle East and Central Asia.
Other holidays occurring around this time include Ostara (amongst neopagans), Chunfen in China, and Vernal Equinox Day (a public holiday in Japan), among others.
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