a date when day and night are of exactly equal length

中文解释

昼夜平分日 The date of the equilux will vary depending on where on Earth you are, whereas the equinox is a fixed instant in time. 昼夜平分点的日期取决于你在地球上所处的位置，而昼夜平分点是一个固定的时间瞬间。