Straight answers, including the unsatisfying ones
These are the questions people actually arrive asking. The answers are short, sourced, and honest about the difference between what is known and what is reconstructed — which, on this subject, is most of it.
When did Jesus die?
No source records the date, so every answer is a reconstruction. The gospels agree the death was on a Friday, before the Sabbath, during Pontius Pilate's prefecture (AD 26-36). Within that window the two dates most often defended are Friday 7 April AD 30 and Friday 3 April AD 33. Both are the output of models with contested assumptions, not records.
Why do scholars narrow it to AD 30 and AD 33?
Not by astronomy alone. The calendar permits more Fridays than two in that window. Scholars narrow the field using non-calendrical evidence: the apparent length of the ministry, John the Baptist beginning in the fifteenth year of Tiberius, and the span of Pilate's office. Those are historical arguments, and no astronomical calculation settles them.
What is 14 Nisan, and why does it matter?
Nisan is the first month of the Hebrew religious year, and Passover falls on 14-15 Nisan. Since Hebrew months begin with the sighting of the new crescent moon, the date moves against the Julian and Gregorian calendars. Working out which Friday the crucifixion fell on means reconstructing when Nisan began in a given year - which is an astronomical question layered on top of a human one.
Why do the gospels disagree about the Passover?
John places the death on 14 Nisan, as the Passover lambs were being slaughtered. The synoptic gospels (Matthew, Mark, Luke) present the Last Supper as a Passover meal, which puts the death on 15 Nisan. This is not a small discrepancy: choosing one over the other changes which years fit. On this site the choice is yours to make, because the disagreement is part of the evidence rather than something to be tidied away.
Was there really an eclipse at the crucifixion?
A partial lunar eclipse did occur over Jerusalem on the evening of 3 April AD 33, and Humphreys and Waddington argued it is the "moon turned to blood" of Acts 2:20. But Schaefer (1990) argued it would have been barely perceptible - never more than about 59% shadowed, with light from the unshadowed part washing out the reddening - and Gonzalez (2022) argued a dust-laden khamsin most likely hid it entirely. There is also a textual objection: Acts is quoting Joel, and darkened sun and bloodied moon are standard prophetic imagery.
Can astronomy prove the date of the crucifixion?
No. Astronomy can tell you precisely when the moon was new. It cannot tell you when the Sanhedrin declared a month to have begun, because that was a human judgement based on sighting the crescent and on the ripeness of the barley, and no record of those decisions survives. Astronomy narrows the field; it does not close it.
Why does Ramadan move through the seasons but Passover does not?
Twelve lunar months run about 354 days, roughly eleven days short of a solar year. The Hebrew calendar corrects for this by inserting a thirteenth month roughly every third year, which keeps Passover in spring. The Islamic calendar deliberately does not correct: intercalation (nasi') was abolished per Qur'an 9:36-37. So Ramadan drifts backwards through all four seasons, completing a circuit in about 33 years.
How accurate are these reconstructions?
The lunar astronomy is accurate to well under a minute. The reconstruction on top of it is accurate to roughly a day - and that last day is exactly the disputed one, because it depends on when a thin crescent was first visible to the naked eye. Change the visibility assumption within a defensible range and the candidate years change with it.
Do I need to be Christian for this to be interesting?
No. The machinery here belongs to no single tradition: it is the Hebrew calendar, the Islamic calendar, and Babylonian and Greek astronomy, all bearing on a question from Roman history. Jewish readers may care most about intercalation, Muslim readers about the abolition of nasi', Christian readers about the Passion chronology, and readers of no faith about how anyone dates an ancient event at all. The site takes no position on what the death of Jesus means - only on what can and cannot be worked out about when it happened.
Still curious?
The instrument on the front page lets you run the calendars yourself and watch the drift that causes all of this. If you would rather read than play, the methodology sets out exactly what is computed and where it stops, and the bibliography lists every work relied on, including the ones that disagree with each other.