I would like to check if my understanding of all this is correct:
The Gregorian Calendar is designed based on the position of the Sun relative to any given point in the Earth (since the calendar considers both days and years).
Because of leap years, the calendar doesn't reflect a perfect loop each calendar year. That is to say, the relative positions are not the same at 12:00am Jan1, 2000 as they were on 12:00 Jan 1, 2001. There is a slight difference because of the time lost or gained depending on the presence of a leap year.
Even if you expand the scope to 200 years, it still doesn't make a perfect loop. This because some centuries have different numbers of leap years in them (2100 will not be a leap year, but 2000 was).
With all this in mind, it actually takes 400 years (as measured by the Gregorian calendar) to make a full loop and and end up where you were before. Midnight Jan 1, 2025 will have the relative positions in the state that they were in at midnight Jan 1, 2021 (because exactly 400 years will have passed, ensuring a uniform number of leap days in the interval).
So, if all this is correct it takes 210,384,000 minutes for our current system of clocks and calendars to line up the solar state with the same state it was 210,384,000 minutes ago.
Does all this look correct to you?
This post was edited by Kayeto on Oct 14 2020 01:27pm