URLs for more research and investigation:
More about Newgrange:
Did the 1752 “Calendar Riots” actually happen?
By the way, as regards that last one: Bear in mind that every science has its lunatic fringe, and for every ninety-five serious archaeoastronomers you’ll find five people absolutely convinced that the Great Pyramid (for example) is not really a fairly secure ancient-religion-based safe-deposit facility, but actually a sooper seekrit mystically aligned GPS waypoint for kindly visitors from Venus or Sirius or wherever who descended from the skies and taught us how to do nearly everything.
When you run across these people’s babblings on the web, please just pass by kindly on the far side while considering (if you like) that any species capable of accidentally discovering blasting gelatine, Silly Putty, the background noise of the Big Bang, Teflon, corn flakes, metallic hydrogen, electromagnetism, and the planet Uranus will have no trouble working out how to build a sand ramp to position heavy stone blocks, or how to use some sticks and string to work out the Earth’s distance to the Sun. I mean, come on now…