First day of fall: Why the equinox isn’t as equal as you might think

(CNN) — Twice a year, the sun doesn’t play favorites. Everyone on Earth is seemingly on equal status — at least when it comes to the amount of light and dark they get.

Your location on the globe also determines whether you mark the day this year on Thursday, September 22, or Friday, September 23. People in the Americas will celebrate it on Thursday; time zone differences mean people in Africa, Europe and Asia will mark it on their Friday.

People really close to the equator have roughly 12-hour days and 12-hour nights all year long, so they won’t really notice a thing. But hardy folks close to the poles, in places such as Alaska and the northern parts of Canada and Scandinavia, go through wild swings in the day/night ratio each year. They have long, dark winters and then have summers where night barely intrudes.

But during equinoxes, everyone from pole to pole gets to enjoy a 12-hour split of day and night. Well, there’s just one rub — it isn’t as perfectly “equal” as you may have thought.

There’s a good explanation (SCIENCE!) for why you don’t get precisely 12 hours of daylight on the equinox. More on that farther down.

But first, here are the answers to your other burning equinox questions:

Where does the word ‘equinox’ come from?

Precisely when does the fall equinox happen?

For people in places such as Toronto and Washington, DC, that’s 9:03 p.m. local time. It comes at 8:03 p.m in Mexico City and Chicago. Out West in San Diego and Vancouver, that means it arrives at 6:03 p.m.

But go in the other direction across the Atlantic Ocean, and the time change puts you into Friday. For residents of Madrid, Berlin and Cairo, it comes at 3:03 a.m. Friday. Going farther east, Dubai marks the exact event at 5:03 a.m.

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