For the Gregorian calendar, the figure is one day in 3,030 years.
The difference in the average length of the year between Julian (365.25 days) and Gregorian (365.2425 days) is 0.002%.
Peter Kreeft in which he examines each of the plausible theories attempting to explain what happened to Jesus at the end of his life, particularly whether he rose from the dead.
Part 1 - 5 Possible Theories that Explain the Resurrection of Jesus Part 2 - Rejecting the Swoon Theory: 9 Reasons Why Jesus Did Not Faint on the Cross Part 3 - Debunking the Conspiracy Theory: 7 Arguments Why Jesus’ Disciples Did Not Lie Part 4 - Refuting the Myth Theory: 6 Reasons Why the Resurrection Accounts are True Part 5 - Real Visions: 13 Reasons the Disciples Did Not Hallucinate Part 6 - (Coming soon!
Even three different witnesses are enough for a kind of psychological trigonometry; over five hundred is about as public as you can wish. 6) that most of the five hundred are still alive, inviting any reader to check the truth of the story by questioning the eyewitnesses—he could never have done this and gotten away with it, given the power, resources, and numbers of his enemies, if it were not true. They were simple, honest, moral people who had firsthand knowledge of the facts.