Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal; the vernal equinox or the autumnal equinox.

 
  • 二分时刻一天中太阳通过天赤道的两个时刻中的任一时刻,此时昼夜长短几乎相等;春分或秋分
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