Question: How do Scientists Set Current Date, Time

[Kilgore Trout]

Above is the official calendar for the Month of September 1752 in England. It's not fake it's real.
By act of parliament September 3 to 13 were erased so that England could abandon the Julian calendar and adopt the Gregorian calendar in effect through most of the world.
So, nobody was born and nobody died in England between September 3, 1752 and September 13, 1752.

The Gregorian calendar was introduced by Pope Gregory in 1582 to deal with problems that arose because it takes 365 days, 5 hours, 48 minutes and 46 seconds for the earth to circle around the sun while our calendars round this time off to 365 days and 6 hours. Over time this created vexing conundrums.

After 1500 years this missing 674 seconds every year was screwing up how the Catholic church wanted to calculate and set the time for Easter.
In 1582 10 days needed to be skipped from history, so that Easter could fall where the church deemed it needed it to fall.
By 1752 the British needed to skip 11 days to get in sync with Gregorian calendar.


Question: Why do we not need to skip a day every hundred years or so so that things sync in with the way nature is. Or is this already being done.
I looked it up on Google and can't figure out how the problem of the missing 674 seconds every year gets dealt with in how calendars are set up.
My guess is, every 125 years or so, July only has 30 days instead of 31, or something along those lines.

 

[JohnHenry]

we have leap year every 4 years 24 times a century and only on the years ending in 00 if the whole 4 digit year js divisible by 400. this makes a year approximately 365.2425 days. consider what would happen if we tried to skip 11 days now.

 

[Kilgore Trout]

we have leap year every 4 years 24 times a century and only on the years ending in 00 if the whole 4 digit year js divisible by 400. this makes a year approximately 365.2425 days. consider what would happen if we tried to skip 11 days now.

Okay, that explains it.
Years ending in 00 are not leap years unless they can be divided by 400. So 2000 was a leap year while 1900, 1800, 1700 were not.
That solves the problem for the most part.
And it explains why some years scientists need to add one more second to the year.
I've heard 680 news say a couple of times that one second needs to be added on to this year at midnight to make clocks sync in with nature.
Thanks for the answer.

 

[basketcase]

Simply put, our divisions of time are based on nature. A day is one cycle of the Earth's rotation while a year is one revolution around the sun. Unfortunately they are not multiples of each other so there is always a little left over. Even more confusing is we defined hours, days, and seconds (we assumed that the Earth wasn't moving) before we had a precise measure for a day resulting in the actual day being a few minutes short of 24 h and we're too stubborn to change.


But no, it would be little problem skipping 11 days. The actual living of life wouldn't change only what name we gave to that day. As long as people had enough notice there wouldn't be any issues.

 

[TeeJay]

@kilgore they actually do dual date so no days are "lost" during the year
But years themselves are totally irrelevant since they are entirely random made up nonsense

@basketcase division of time was never based on nature (as can be seen by how far calendars skip out of sync with seasons, eg Roman or Islamic calendars)
Things like 8 day weeks and 20 month years were very common back in the day. Romans in particular (which is what Gregorian calendar was based off) insisted on using even numbers (eg 10 months) for "precision"

Our original calendars were all LUNAR based which was even worse since very irregular cycles

 

[basketcase]

...

@basketcase division of time was never based on nature (as can be seen by how far calendars skip out of sync with seasons, eg Roman or Islamic calendars)
Things like 8 day weeks and 20 month years were very common back in the day. Romans in particular (which is what Gregorian calendar was based off) insisted on using even numbers (eg 10 months) for "precision"

Our original calendars were all LUNAR based which was even worse since very irregular cycles

Is the moon not part of nature? And are you saying a day isn't based on the rising of the sun or that the year isn't based on the repetition of seasons?

And yes, the natural cycle of the moon, the Earth's rotation, and revolution around the sun not syncing up is the reason for the irregularities.

 

[explorerzip]

Our original calendars were all LUNAR based which was even worse since very irregular cycles

Lunar calendars are only irregular when compared to the Gregorian calendars. They weren't so irregular when they were in normal use.

Further, the concept of date and time is arbitrary. There's no scientific reason why there needs to be 60 minutes in an hour, 24 hours in a day, 12 months in a year, etc. We divided time that way because it was convenient and simple to understand.

 

[FAST]

I think the whole world, except the US,... should adopt metric time,... that would really piss of our neighbours to the south.

A little trivia, anybody know why the line frequency in North America is 60 HZ,... ???

And what it was before becoming 60 HZ,...???

 

[benstt]

Lunar calendars are only irregular when compared to the Gregorian calendars. They weren't so irregular when they were in normal use.

Lunar calendars and solar calendars are ultimately irregular when compared to each other. The time for the moon to circle the earth is not cleanly divisible into the time it takes for the earth to go around the sun, and neither fit cleanly with the time it takes for the Earth to rotate.

 

[MissCroft]

But no, it would be little problem skipping 11 days. The actual living of life wouldn't change only what name we gave to that day. As long as people had enough notice there wouldn't be any issues.

Back in 1752, there were riots with people demanding their eleven days back.


I would think people would be pissed off if their birthdays got skipped over. LOL And nowadays it would definitely be a problem for scheduled work/medical appointments. There would have to be a LOT of notice.

 

[oldjones]

Simply put, our divisions of time are based on nature. A day is one cycle of the Earth's rotation while a year is one revolution around the sun. Unfortunately they are not multiples of each other so there is always a little left over. Even more confusing is we defined hours, days, and seconds (we assumed that the Earth wasn't moving) before we had a precise measure for a day resulting in the actual day being a few minutes short of 24 h and we're too stubborn to change.


But no, it would be little problem skipping 11 days. The actual living of life wouldn't change only what name we gave to that day. As long as people had enough notice there wouldn't be any issues.

However there are stories of upset and even riots in England as people fretted over everything from bets to leases. Not to mention that the preceding year, 1751 was only 282 days long, as it began on March 25, the old-style New Year (still observed in 'fiscal years') but ended on the new style December31. There's a Hogarth painting of a riotous post-election night, showing a 'Give us back our eleven days' placard underfoot on the floor.

It took those eccentric Brits more than a century and a half to catch up to Europe, who pretty much all switched when Gregory said to in 1582. But the Russians didn't until the Bolshies forced them in 1918, and the Greeks and Turks held out until the 1920s.

 

[explorerzip]

Lunar calendars and solar calendars are ultimately irregular when compared to each other. The time for the moon to circle the earth is not cleanly divisible into the time it takes for the earth to go around the sun, and neither fit cleanly with the time it takes for the Earth to rotate.

The orbit of the planets is not constant so the time taken will never be cleanly divisible.

 

[explorerzip]

Back in 1752, there were riots with people demanding their eleven days back.


I would think people would be pissed off if their birthdays got skipped over. LOL And nowadays it would definitely be a problem for scheduled work/medical appointments. There would have to be a LOT of notice.

I imagine that people also were not happy when George W. Bush changed the daylight savings time to start earlier and end later in the year.

 

[Kilgore Trout]

I just did a bit of reading on leap seconds.
Because the earth's rotation is slowing down due to drag from the moon's gravity, 27 leap seconds have had to be added to coordinated universal time since 1972.
The last second added was on Dec 31/2016.

The last minute of a day where a leap second is added on is 61 seconds long and this has caused some computer systems around the world synced in with UTC time to crash.

When the dinosaurs were here a day was 23 hours long and 100 million years from now, if anyone is still around here, a day will be 25 hours long due to the earth's rotation gradually slowing down.

Calendars would need to be altered somehow because it would take the same amount of time to rotate around the sun; but, it would happen in, say 350 days, instead of 365.25 days.

 

[oldjones]

The orbit of the planets is not constant so the time taken will never be cleanly divisible.

On the other hand, we all know the difference between yesterday, today and tomorrow. And we can cope quite well, until some troublemaker wants to define when to-day is officially over and your library books are late. That's the sort of occasionwhen the vague days of the calendar you scratched on the wall of your cell hafta line up with what the Atomic clock in Colorado (or the Warden's watch) says.

Like the Catholic church — who had feast day offerings to collect — you can postpone dealing with the mismatch for a century or so, but after a millennium, the errors add up. And you can't ignore a whole week and a half.

The part to really marvel at is that in an era before accurate clocks, the astronomers and mathematicians of the time could work out the length of solar year to within a minute.

 

[jcpro]

Which reminds me, best wishes for the 5778.

 

[ets2361]

I thought Dec 31/2016 seemed like a really long day. That extra second really threw me off. It took me many milliseconds to recover.

 

[basketcase]

Which reminds me, best wishes for the 5778.

I love the Jewish calendar. A leap month that they couldn't even give an original name to. It's like every 4 years having Feb. 28th followed by Feb. 28th. But I guess it gets the job done.

 

[Submariner]

A little trivia, anybody know why the line frequency in North America is 60 HZ,... ??? And what it was before becoming 60 HZ,...???

Long story, hard to give short answer. Lots of technical evolution, compromising efficiency for different end uses, competition, precedence, etc. One story suggests that Tesla successfully argued with Westinghouse engineers for 60 Hz as most efficient for electric motors and power distribution in his day, and thereafter a slow standardization began in US and Canada. In the late 1800's the early power generation projects on the American side of the Niagara River produced 25 Hz, as did a number of the earliest generating stations in Ontario. In Ontario, there was still some 25 Hz industrial load in operation until 2009 which was supported by a couple of 25 Hz generators at Beck 1 generating station.

Also, note that the system is not always operated at 60.00 Hz. There are times when Balancing Authorities will slow or speed up the grid by as much as 20 mHz for time error correction.

 

[HungSowel]

I am guessing that the difference was picked such that an european made generator/motor would not be compatible with US standards and vice versa as a means of market protection.

Edison at the time was petitioning for a DC transmission system, carrying probably what I guess would be 24V. His argument was that lower DC voltage was not a shock hazzard, and went on tour electricuting animals with 120V AC power to prove the dangers of Tesla's proposal. Tesla's AC system was much much cheaper to implement and had much lower power losses, so for the sake of economics rather than public saftey, Tesla won.