h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I notice Google has an animated title today, celebrating Newton's Birthday. Newton himself was very proud of the fact that he was born on Christmas Day, 1642. So why the confusion?

It's because the UK and the northern countries of Europe used a different calendar from the southern countries of Europe at the time. It was indeed 25 December 1642 in England, but it was already 4 January 1643 in Rome.

The Roman calendar ("Gregorian") was eventually adopted in the UK and in the rest of the world, but not until after Newton had died. So I think we should continue to celebrate Newton's birthday on 25th December, as he did.

Not sure I agree, but you've got me wondering if people adjusted their birthdays when the Gregorian calendar came in or stuck with the same date.

If we celebrated it on Dec 25, then the earth will not quite have made it around the sun an exact number of times since Newton's birth.

These things are important, apparently.

Especially if the number of orbits is divisible by both 2 and 5.

And if the number of orbits is divisible by both 2 squared and 5 squared, then we might need to pack some spare underclothes.

Well, the Battle of the Boyne was on 1 July, and it is now commemorated in Northern Ireland every year on 12 July (it's a public holiday). So some things at least changed date when the calendar changed. But Christmas Day remained on 25 December. Nobody moved it to January.

You mean we go on impromptu journeys every ten years?

Other significant dates fall on the 24th or 25th of a month: St John's Day (24 June, opposite to Christmas) and the old new year (25 March). What was significant about a week before the end of a month? Has it something to do with pretending that a month equalled a lunar month?

I'm sure you already have an entry in explaining all these and other questions . . . I love the explanation of the fiscal year starting on 5 or is it 6 April.

The 25th's were the quarter days because they were considered to be the middles of the corresponding seasons. 25th June was traditionally called "Midsummer's Day".

I think they were:

25 March Ladymas
25 June Johnsmas
25 September Michaelmas
25 December Christmas

"But Christmas Day remained on 25 December. Nobody moved it to January."

Since it'd been 25 December for so long it had effectively drifted. The new calendar put it right.

The stuff about the quarter days is interesting. Does that mean that in the Julian calendar the 25th was originally the actual solstice?

I don't know.