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Use "spring equinox" in a sentence
"The need for this intercalation was, at the time of Christ, still determined empirically, in such a way that the celebration of the Pasch at the full moon or fourteenth day of the first month, Nisan, should always occur after the spring equinox (Mar. 21st)."
"This happens twice a year, and the times when the sun passes the equator are called the vernal or spring equinox and the autumnal equinox respectively."