Are both correct? If only one is, which is it. Either way, why?
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The Earth rotates around the sun in 365.256 days, this is called a Sidereal year.
But there is also a Tropical Year which is 365.2422 days long, this is the time between Vernal Equinoxes or equivalent. This is how long it takes for the Seasons to repeat
For the sidereal year, draw a line from the Sun to Alpha Centauri and when the Earth crosses that line your year begins and when it crosses it again your year ends. Nice and simple and what you traditionally think of as a year
For a tropical year you measure from when the sun crosses the equator going northward until it crosses the equator going northward again, but because the Earth is tilted and this tilt changes a bit every year the tropical year ends up being different. If you were to set your line in the first example such that the north pole of the Earth is also pointed towards Alpha Centauri then every rotation you’d notice that the North Pole was pointed a bit further away and after about 12,900 years you’ll see its pointed almost directly away from Alpha Centauri when it crosses the line, and after 25,772 years it will complete its cycle and be pointed directly back at Alpha Centauri at the start of a new year.
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