Yesterday and today (September 22 and 23) are ‘Equinox’ days. This means that day and night are exactly 12 hours apart. The Sun travels exactly along the Equator twice a year (March 20-21, September 22-23), so that the whole of the earth would experience hours of equal day and night.
This phenomenon is called Equinox.Apparently, the Equinox which occurs in September marks the beginning of the Autumn season in the Northern hemisphere while it is the beginning of the Spring season in the southern hemisphere. This can occur any time between September 21 and September 24. This year, it will occur at 12:51 am on September 23, according to NASA.