23 September

September 23 is the 266th day of the year (267th in leap years) in the Gregorian calendar. There are 99 days remaining until the end of the year. This date is slightly more likely to fall on a Wednesday, Friday or Sunday (58 in 400 years each) than on Monday or Tuesday (57), and slightly less likely to occur on a Thursday or Saturday (56). It is frequently the day of the autumnal equinox in the Northern Hemisphere and the day of the vernal equinox in the Southern Hemisphere.

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Wikipedia