equinox
/ˈikwəˌnɑks/
noun
- Either of the two times each year when day and night are of equal length, occurring in March (vernal equinox) and September (autumnal equinox).
- On the equinox, the Sun rises exactly in the east and sets exactly in the west.
- The spring equinox marks the beginning of longer days and warmer weather.
- Many cultures celebrate festivals around the autumnal equinox to give thanks for the harvest.