Why Leap Years Exist: Orbital Remainder (3D)

Earth's real orbit around the Sun takes 365.2422 days, not an even 365 — and that leftover fraction is the entire reason leap years exist. This simulation runs Earth around a real orbit at its true period while a separate calendar counter ticks off years using whichever rule you select: no correction at all, the simple Julian "every 4 years" rule, or the real Gregorian rule (leap every 4 years, except century years unless divisible by 400). Each time the calendar rolls over to a new year, a marker is dropped at Earth's true orbital position at that instant — with no correction the markers visibly crawl around the ring year after year, while the Gregorian rule keeps them locked almost exactly in place, correcting the drift down to about one day every 3,216 years.