Sunday 23rd September at 02.54 is the Pagan Celebration of the Autumn Equinox, marking the time of harvest festival and fulfilment of summer; since, in the Northern Hemisphere, from now on there will be more dark than light for the rest of the year.
An equinox is an astronomical event when the plane of Earth's equator passes the center of the Sun. Equinoxes occur twice a year, around 21st March and 22nd/23rd September.
At this point in the year, the night and day lengths are exactly equal, so it's a time of balance and a good time for introspection, look for what is good and worthwhile to become seeds for next year.
Here in the UK, followers of the Druids, Pagans, Celtic and Gaelic traditions, as well as Wicca religion, gather at megalithic stone circles such as Stonehenge (Near Salisbury, Wiltshire) and Castlerigg (Keswick, Cumbria), to celebrate and watch the equinox sunrise.
Sunday 23rd September is the start of Sukkot, the Jewish feast of the Tabernacles, it celebrates the harvest and the preservation of the Israelites in the wilderness.
Jewish feast dates begins at sundown of the night beforehand. Thus all holiday observances begin September.