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Comment by jefftk | Hacker News Reader

Astronomers have been one of the groups most vocal in favor of retaining leap seconds: https://www.nature.com/articles/423671a

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Astronomers may just understand that the problem exists: [the ITU group’s chairman] says he needs more input from people who use universal time. “Many people don't even know that leap seconds exist,”

The decision to ignore leap seconds reminds of the decision by Russian and some other orthodox churches to ignore changes introduced by Gregorian calendar. The decision saved them some internal political problems, like the need to decide which saints will have their celebrations missing, but now the Orthodox Christmas is moving to summer with the speed of about 1 day per 100 years. Eventually somebody will have to deal with this, but not now - there’s a lot of time - same thinking.

Meanwhile, if you leave in a Gregorian country you can have your Christmas tree for free on Orthodox December 12th…

Orthodox Christians in the Southern Hemisphere already celebrate Christmas in summer, as do other Christians.

#borealocentrism

> borealocentrism

Guilty as charged. Thinking of that - there could be no more Russian winter as we used to it at all, even in the Northern hemisphere. My friends are now growing apricots in the Russian temperate zone. Apricots! - in the place there the “Baptismal Frosts” (to happen each year just before Christmas) used to kill all such fancy vegetation.

#climateasitwasbeforechangecentrism

> Eventually somebody will have to deal with this

The Islamic calendar drifts by about 10 days a year, and Muslims seems to be able to cope fine with their holidays not consistently being in the same season.

Well to be fair, I don't think the Muslim calendar is _meant_ to have any solar correspondence anyway. But more importantly the holidays, is the use of the calendar in having a natural sense of time (that is, corresponding with the seasons / sun). Which is why most Islamic countries use the Gregorian calendar for civil purposes (or so claims Wikipedia, at least).

Many Islamic countries do in fact use the Gregorian calendar for Civic purposes, at the very least Egypt does which I can confirm by virtue of living here.

Orthodox Christian countries also use the Gregorian calendar for civil purposes.

I'm not sure Orthodox Christians celebrate Christmas with a tree. At least in Russia the tree is mounted for New Year celebration and it lasts till Orthodox Christmas for granted. Actually it usually lasts to the so-called Old New Year - New Year in Old Style (meaning Julian Calendar before introduction of Gregorian one by Bolsheviks).

Far from being "most vocal", that 2003 article has a single quote from a single astronomer whose only warning is:

> If the change is implemented, “the old meaning of time will become ambiguous,” warns Steve Allen, an astronomer at the Lick Observatory in Santa Cruz, California.

This does seem like a problem that is solvable.

In 2015 the ITU (mentioned in that 2003 story as studying the problem) announced:

> The ITU World Radiocommunication Conference (WRC-15), currently in session in Geneva from 2 to 27 November, has decided that further studies are required on the impact and application of a future reference time-scale, including the modification of coordinated universal time (UTC) and suppressing the so-called “leap second”

https://www.itu.int/net/pressoffice/press_releases/2015/53.a...

In 2012 they also decided to defer:

> ITU Press Release of 19 January 2012 - ‘ITU Radiocommunication Assembly defers decision to eliminate the leap second’

https://www.itu.int/en/ITU-R/Documents/ITU-R-FAQ-UTC.pdf

> If the change is implemented, “the old meaning of time will become ambiguous,” warns Steve Allen, an astronomer at the Lick Observatory in Santa Cruz, California.

I'm with Allen. It's fine to drop leap-seconds; but then it's not UTC any more, it's a new time scale, and it needs a new name.

We've made this mistake before: in fact GMT has been redefined many times, and as a result the time interval between two GMT timestamps depends on which versions of GMT the two timestamps use, and so on the dates of the timestamps.

Allen has an instructive page on time scales here: https://www.ucolick.org/~sla/leapsecs/timescales.html

> a single quote from a single astronomer whose only warning is...

It's not a quote, but the article also has Allen saying that "it could cost between US$10,000 and US$100,000 for each telescope to correct the problem, and that corrections will be tricky to implement."

It also has another astronomer claiming problems: "But separating time from rotation would mean that telescopes would no longer function properly, according to Patrick Wallace, an astronomer at the Rutherford Appleton Laboratory in Oxford, UK. Most telescopes with a viewfinder wouldn't be immediately affected, but instruments that track satellites and other moving objects could feel the effects within a few years, Wallace warns."

I found a few more details: https://news.ycombinator.com/item?id=32232564

It sounds like FB/Meta is correct in saying that Astronomers did object. I'd suggest (like Mata does) those objections are not especially important considering the trade-offs though.

Astronomers use time for at least two different thing. For recording the time of events and observations, astronomers usually use the julian day, and for that leap seconds are a big pain. However, for precisely pointing a telescope without a viewfinder, you need the local sidereal time. The local sidereal time is fairly straightforward to (approximately) compute from UT1, the current date and your longitude. And leap seconds keep UTC within 1 second of UT1, so you can just use UTC.

But, for the latter problem, a better solution would probably be to have a service similar to NTP, that gives the current Greenwhich sidereal time, rather than UTC. Then it could be corrected more often than the current leap seconds. That doesn't solve the problem for existing telescope systems though.

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