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UTC is (as everyone knows) a bit problematic due to leap seconds. Different software systems handle the leap seconds somewhat differently. Handling leap seconds

by nawitus 11y ago

UTC is (as everyone knows) a bit problematic due to leap seconds. Different software systems handle the leap seconds somewhat differently. Handling leap seconds is is actually quite difficult if you want to get it absolutely correct. In 99% of cases the problems are just ignored (e.g. "it doesn't matter if the chart is slightly odd looking when you look at the moment of the leap second"). There's also the problem that every software using UTC must be updated at least once every six months. That may be a lesser problem these days, but is still somewhat relevant especially in various industries. I'd probably go with TAI and just convert the dates to the "human readable" format in the UI. Of course, that's not trivial either.

johnchristopher 11y ago
For those who don't know about TAI: https://en.wikipedia.org/wiki/International_Atomic_Time https://en.wikipedia.org/wiki/International_Atomic_Time International Atomic Time (TAI, from the French name Temps Atomique International[1]) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid.[2] It is the basis for Coordinated Universal Time (UTC), which is used for civil timekeeping all over the Earth's surface, and for Terrestrial Time, which is used for astronomical calculations. As of 30 June 2015 when the last leap second was added,[3] TAI is exactly 36 seconds ahead of UTC. The 36 seconds results from the initial difference of 10 seconds at the start of 1972, plus 26 leap seconds in UTC since 1972. Time coordinates on the TAI scales are conventionally specified using traditional means of specifying days, carried over from non-uniform time standards based on the rotation of the Earth. Specifically, both Julian Dates and the Gregorian calendar are used. TAI in this form was synchronised with Universal Time at the beginning of 1958, and the two have drifted apart ever since, due to the changing motion of the Earth.
readstoomuch 11y ago
Was ist GoogleTime?
- JD557 11y ago
  I don't have a source at hand but, IIRC, instead of having leap seconds, Google slightly dilates each second to compensate for that. The time eventually corrects itself.
feld 11y ago
Easy, we just kill off the idea of leap seconds. Someone please convince Russia and UK to agree so we can do it.
- LeoPanthera 11y ago
  No thank you. Just store times on computers as $epoch+$offset and then convert to UTC when displayed to the user. That way, only the display routine has to care about leap seconds and it won't break anything.
  - repsilat 11y ago
    If you mean "UNIX time", you'll be disappointed -- UNIX time is not the number of seconds since the epoch, it is also leap-second adjusted. It stops when a leap second happens to make sure there are exactly 86400 UNIX seconds between every midnight (so you can do divmod calculations on timestamps.) Maybe you were suggesting an improvement to UNIX time, though, in which case I think the grandparent and I would get behind your proposal.
    - LeoPanthera 11y ago
      Yeah I know about unix time and that isn't what I meant. It never made sense to me. Just have a monotonic timer and an epoch, and worry about UTC and leap seconds in the view.
- cbd1984 11y ago
  > Easy, we just kill off the idea of leap seconds. OK, now everyone who cares how much time has passed in terms of the Earth's rotation needs to keep a time separate from everyone else. Astronomers come to mind, for example.
  - repsilat 11y ago
    If anyone needs to know about the Earth's rotation that precisely they probably - don't rely on their laptop's system clock, - don't use UTC either because of minor rotational noise/drift and the discontinuity around the leap-second, and - find the whole 24-hour clock thing a little useless, not being seasonally adjusted etc. I bet they'd prefer TAI to UTC (or even "Google time"), because they've probably got their own timekeeping systems that will probably interact more smoothly (heh) with it. More to the point, there are approximately zero astronomers on Earth, and approximately seven billion non-astronomers. Even if astronomers do prefer UTC, it's better to make them have their own systems to add or subtract twenty-something seconds from TAI than forcing all of my timekeeping devices to have a database of historical leap-seconds and an internet connection to hear about new ones. Not to mention the fact that I can't write down what the time will be in UTC in 86400 * 1000 seconds... Absolutely ridiculous.
ymse 11y ago
I'd be happy just to get rid of DST.
- minikites 11y ago
  DST is great and the reasons I think that are nicely summed up here: http://www.leancrew.com/all-this/2013/03/why-i-like-dst/ http://www.leancrew.com/all-this/2013/03/why-i-like-dst/ > If we stayed on Standard Time throughout the year, sunrise here in the Chicago area would be between 4:15 and 4:30 am from the middle of May through the middle of July. > If, by the way, you think the solution is to stay on DST throughout the year, I can only tell you that we tried that back in the 70s and it didn’t turn out well. Sunrise here in Chicago was after 8:00 am, which put school children out on the street at bus stops before dawn in the dead of winter.

by nawitus 11y ago

johnchristopher 11y ago

For those who don't know about TAI: https://en.wikipedia.org/wiki/International_Atomic_Time https://en.wikipedia.org/wiki/International_Atomic_Time International Atomic Time (TAI, from the French name Temps Atomique International[1]) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid.[2] It is the basis for Coordinated Universal Time (UTC), which is used for civil timekeeping all over the Earth's surface, and for Terrestrial Time, which is used for astronomical calculations. As of 30 June 2015 when the last leap second was added,[3] TAI is exactly 36 seconds ahead of UTC. The 36 seconds results from the initial difference of 10 seconds at the start of 1972, plus 26 leap seconds in UTC since 1972. Time coordinates on the TAI scales are conventionally specified using traditional means of specifying days, carried over from non-uniform time standards based on the rotation of the Earth. Specifically, both Julian Dates and the Gregorian calendar are used. TAI in this form was synchronised with Universal Time at the beginning of 1958, and the two have drifted apart ever since, due to the changing motion of the Earth.

readstoomuch 11y ago

Was ist GoogleTime?

JD557 11y ago
I don't have a source at hand but, IIRC, instead of having leap seconds, Google slightly dilates each second to compensate for that. The time eventually corrects itself.

feld 11y ago

Easy, we just kill off the idea of leap seconds. Someone please convince Russia and UK to agree so we can do it.

LeoPanthera 11y ago
No thank you. Just store times on computers as $epoch+$offset and then convert to UTC when displayed to the user. That way, only the display routine has to care about leap seconds and it won't break anything.
- repsilat 11y ago
  If you mean "UNIX time", you'll be disappointed -- UNIX time is not the number of seconds since the epoch, it is also leap-second adjusted. It stops when a leap second happens to make sure there are exactly 86400 UNIX seconds between every midnight (so you can do divmod calculations on timestamps.) Maybe you were suggesting an improvement to UNIX time, though, in which case I think the grandparent and I would get behind your proposal.
  - LeoPanthera 11y ago
    Yeah I know about unix time and that isn't what I meant. It never made sense to me. Just have a monotonic timer and an epoch, and worry about UTC and leap seconds in the view.
cbd1984 11y ago
> Easy, we just kill off the idea of leap seconds. OK, now everyone who cares how much time has passed in terms of the Earth's rotation needs to keep a time separate from everyone else. Astronomers come to mind, for example.
- repsilat 11y ago
  If anyone needs to know about the Earth's rotation that precisely they probably - don't rely on their laptop's system clock, - don't use UTC either because of minor rotational noise/drift and the discontinuity around the leap-second, and - find the whole 24-hour clock thing a little useless, not being seasonally adjusted etc. I bet they'd prefer TAI to UTC (or even "Google time"), because they've probably got their own timekeeping systems that will probably interact more smoothly (heh) with it. More to the point, there are approximately zero astronomers on Earth, and approximately seven billion non-astronomers. Even if astronomers do prefer UTC, it's better to make them have their own systems to add or subtract twenty-something seconds from TAI than forcing all of my timekeeping devices to have a database of historical leap-seconds and an internet connection to hear about new ones. Not to mention the fact that I can't write down what the time will be in UTC in 86400 * 1000 seconds... Absolutely ridiculous.

ymse 11y ago

I'd be happy just to get rid of DST.

minikites 11y ago
DST is great and the reasons I think that are nicely summed up here: http://www.leancrew.com/all-this/2013/03/why-i-like-dst/ http://www.leancrew.com/all-this/2013/03/why-i-like-dst/ > If we stayed on Standard Time throughout the year, sunrise here in the Chicago area would be between 4:15 and 4:30 am from the middle of May through the middle of July. > If, by the way, you think the solution is to stay on DST throughout the year, I can only tell you that we tried that back in the 70s and it didn’t turn out well. Sunrise here in Chicago was after 8:00 am, which put school children out on the street at bus stops before dawn in the dead of winter.