equinox
US
UK equinox n: (date when day and night are equal)
SC 昼夜平分点 zhòu yè píng fēn diǎn
SC 春分或秋分 zhòu yè píng fēn diǎn，chūn fēn huò qiū fēn
Ancient cultures are said to have held ceremonies during the equinoxes.
autumnal equinox n: (first day of the fall season)
SC 秋分（点） qiū fēn diǎn
vernal equinox n: (point when sun is across equator)
SC 春分（点） chūn fēn diǎn
The vernal equinox occurs each March and heralds the arrival of Spring.