On the day of an equinox, the day and the night have exactly the same duration. Every year the event occurs on two dates, at the same time a new season starts. Around the 19th, 20th and 21st of March begins the spring and around the 22nd, 23rd and 24th of September the autumn. In astronomy, the equinox is determined not just with a date, but with a precise time. This year, the sun is at the autumnal equinox on September 23 at 03:53 of Central European summer time.