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Gregorian Calendar Correction to Vernal Equinox Date

-- paul | October 27, 2021

Question:

One of the Ask the Astronomer questions was about the the vernal equinox of 3000 bc. The answer was that it was on April 15th. I’m confused because I thought the Gregorian calendar corrected itself to keep the the equinox near March 20 or 21. Can you explain this to me?

-- paul

Answer:

You are correct in that when the Gregorian calendar was adopted in 1545 that the date of the vernal equinox was set such that it would occur in mid-March going forward. This, of course, was after the 3000 BCE date requested in the previous post.

-- Jeff Mangum

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