Astronomers have calculated that Christmas should be in June, by charting the appearance of the 'Christmas star' which the Bible says led the three Wise Men to Jesus.
They found that a bright star which appeared over Bethlehem 2,000 years ago pinpointed the date of Christ's birth as June 17 rather than December 25.
The researchers claim the 'Christmas star' was most likely a magnificent conjunction of the planets Venus and Jupiter, which were so close together they would have shone unusually brightly as a single "beacon of light" which appeared suddenly.
If the team is correct, it would mean Jesus was a Gemini, not a Capricorn as previously believed.
Australian astronomer Dave Reneke used complex computer software to chart the exact positions of all celestial bodies and map the night sky as it would have appeared over the Holy Land more than 2,000 years ago.
It revealed a spectacular astronomical event around the time of Jesus's birth.
Mr Reneke says the wise men probably interpreted it as the sign they had been waiting for, and they followed the 'star' to Christ's birthplace in a stable in Bethlehem, as described in the Bible.
Generally accepted research has placed the nativity to somewhere between 3BC and 1AD.
Using the St Matthew's Gospel as a reference point, Mr Reneke pinpointed the planetary conjunction, which appeared in the constellation of Leo, to the exact date of June 17 in the year 2BC.
The astronomy lecturer, who is also news editor of Sky and Space magazine, said: "We have software that can recreate exactly the night sky as it was at any point in the last several thousand years.
"We used it to go back to the time when Jesus was born, according to the Bible.
"Venus and Jupiter became very close in the the year 2BC and they would have appeared to be one bright beacon of light.
"We are not saying this was definitely the Christmas star - but it is the strongest explanation for it of any I have seen so far.
"There's no other explanation that so closely matches the facts we have from the time.
"This could well have been what the three wise men interpreted as a sign. They could easily have mistaken it for one bright star.
"Astronomy is such a precise science, we can plot exactly where the planets were, and it certainly seems this is the fabled Christmas star."
Mr Reneke, formerly the chief lecturer at the Port Macquarie Observatory in New South Wales, added: "December is an arbitrary date we have accepted but it doesn't really mean that is when it happened.
"This is not an attempt to decry religion. It's really backing it up as it shows there really was a bright object appearing in the East at the right time.
"Often when we mix science with religion in this kind of forum, it can upset people. In this case, I think this could serve to reinforce people's faith."
Previous theories have speculated the star was a supernova - an exploding star - or even a comet. But Mr Reneke says by narrowing the date down, the technology has provided the most compelling explanation yet.