when is the last day of summer in 2023

The last day of summer in 2023, according to the astronomical definition (which is based on the summer solstice and the autumnal equinox), is Friday, September 22, 2023. Summer 2023 officially ends on this date, with autumn starting on Saturday, September 23, 2023. Meteorological summer, which is based on calendar months, ends earlier on August 31, 2023, but the astronomical summer lasts until September 22, 2023.