Autumnal Equinox 2021
This illustration by Tau’olunga via Wikimedia Commons shows the day arc of the equinox sun, as seen from Earth’s equator. Also showing are twilight suns (in red) down to -18 degrees altitude. Note that the sun is at its highest point at noon. And see that the tree’s shadow at noon is cast straight down. That is – as seen from the equator on the day of an equinox – a tree stands in the center of its own shadow.
Equinox comes on September 22
The equinox arrives on September 22, 2021, at 19:21 UTC. That’s when the equinox sun is exactly above Earth’s equator, moving from north to south. At the equinox, days and nights are approximately equal in length. For us in the Northern Hemisphere, the sun is rising later now, and nightfall comes sooner. We’re enjoying the cooler days of almost-autumn.
Meanwhile, south of the equator, spring begins.
Although the equinox happens at the same moment worldwide (at 19:21 UTC on September 22), your clock time depends on your time zone. For time zones in the continental U.S., this equinox comes during the daylight hours on September 22 (3:21 p.m. EDT, 2:21 p.m. CDT, 1:21 p.m. MDT and 12:21 p.m. PDT). Translate UTC to your time.
Autumnal Equinox 2021
This illustration by Tau’olunga via Wikimedia Commons shows the day arc of the equinox sun, as seen from Earth’s equator. Also showing are twilight suns (in red) down to -18 degrees altitude. Note that the sun is at its highest point at noon. And see that the tree’s shadow at noon is cast straight down. That is – as seen from the equator on the day of an equinox – a tree stands in the center of its own shadow.
Equinox comes on September 22
The equinox arrives on September 22, 2021, at 19:21 UTC. That’s when the equinox sun is exactly above Earth’s equator, moving from north to south. At the equinox, days and nights are approximately equal in length. For us in the Northern Hemisphere, the sun is rising later now, and nightfall comes sooner. We’re enjoying the cooler days of almost-autumn.
Meanwhile, south of the equator, spring begins.
Although the equinox happens at the same moment worldwide (at 19:21 UTC on September 22), your clock time depends on your time zone. For time zones in the continental U.S., this equinox comes during the daylight hours on September 22 (3:21 p.m. EDT, 2:21 p.m. CDT, 1:21 p.m. MDT and 12:21 p.m. PDT). Translate UTC to your time.