U.S. Moves to Kill Leap Seconds 601
blacklite001 writes "Not content with merely extending Daylight Savings Time, the U.S. government now also proposes to eliminate leap seconds, according to a Wall Street Journal story. Their proposal, 'made secretly to a United Nations body,' includes adding 'a "leap hour" every 500 to 600 years.'
Hey, anyone remember the last bunch of people to mess with the calendar?"
More info (Score:5, Informative)
Apparently not... (Score:5, Informative)
Big leap of faith... (Score:5, Informative)
I actually agree that leap seconds are a bit of a mess, and I wouldn't mind seeing a better solution. But the one proposed sounds a bit bizarre. Surely the real problem is an artifact of the infancy of computer systems and the ad hoc, non-general solutions to time representation we've been using due to very small address spaces that are rapidly falling by the wayside. Why not just delay the issuing of them for a couple of decades until we can think harder about the problem. Pretending that any law passed now is going to stand unused for hundreds of years before it has any effect seems a little
Re:The _last_ bunch? (Score:2, Informative)
Re:now correct me if im wrong (Score:5, Informative)
The second is one of the fundamental units in the metric system. Many other units and constants are based on the second. For example, the speedometer in your car shows miles per hour, the speed of light is given in meters per second, etc. If we changed the value of the second, then either:
a. We'd be forcing the world scientific community to relearn an entire set of new constants, or, more likely,
b. There would be two definitions of the 'second', the US definition and the scientific definition.
I don't think either of these is really what we want.
Re:neat bit (Score:3, Informative)
(also note that this ends 61, about the time atomic clocks became usable)
Re:Planet (Score:3, Informative)
Re:Hmm... (Score:5, Informative)
Section 8, Clause 5: To coin Money, regulate the Value thereof, and of foreign Coin, and fix the Standard of Weights and Measures
Time is a measure, therefore they actually do thave the authority to regulate it.
Re:Really Good Reference on Time (Score:4, Informative)
This has everything you mentioned above, plus some very current research, the role of the USNO in the GPS satellite constellation, and even the history of timekeeping in the USA. On the whole an excellent resource to look at if you want to know more about time.
Whenever I setup a new system, I usually drop by their "what time is it" to set the clocks on systems (especially if I don't want to download or enable a nettime client). It will get you the correct time +/- 30 seconds with the web interface, which is as good or better than most casual users really care to get it anyway. Usually far more accurate than most people's watches as well.
Re:Apparently not... (Score:4, Informative)
Re:Good question from a lazy asker... (Score:4, Informative)
Re:Apparently not... (Score:4, Informative)
Re:Apparently not... (Score:3, Informative)
Re:I don't see how the problem occurs (Score:3, Informative)
Re:now correct me if im wrong (Score:3, Informative)
It doesn't actually work. It is slowly (VERY SLOWLY) but surely moving off, because the leap month isn't adjusting exactly how much it needs to. I was surprised when I heard this, too - but someone I know programmed one of the Hebrew calendars (it uses GPS coords to calculate exact sunset - quite nice), and showed me the math. Turns out things end up misaligning ala the Islamic calendar, but only after a very long time from now.
Now, the reason it _used_ to work is that the rabbinical court ("beis din") in Jerusalem would just not listen to witnesses about the sighting of the new moon until they felt like it - and if things were starting to get dicey, they'd just not hear it until the next day or something.
The Jewish calendar is lunar _based_. It is not actually a strict lunar calendar due to the human intervention possible in it. I don't think it's a great choice for system time-keeping.
-Erwos (who's a for-real Orthodox Jew)
Re:Apparently not... (Score:3, Informative)
There are many perfectly valid arguments against leap seconds. The difficulty in calculating the exact number of seconds between two events, the fact that calculations involving future times can give different results after leap seconds are declared, the difficulty of dating events that occur near or during leap seconds, all are serious drawbacks.
But these are not good arguments for removing leap seconds from UTC! Why do that when you can choose from two perfectly good standard time scales that don't have leap seconds? Those are the GPS (Global Positioning System) time scale and the TAI (International Atomic Time) timescale. They differ by a fixed offset: TAI is 19 seconds ahead of GPS and will remain so despite any future leap seconds added to UTC. (Strictly speaking the offset between TAI and GPS typically varies by some tens or hundreds of nanoseconds around 19 seconds, but the GPS system operators try to drive that error to zero, and they publish those offsets. The big advantage of GPS time, of course, is its ready availability from inexpensive receivers.)
CDMA digital cellular is one system that chose the GPS timescale to avoid the nasty discontinuities associated with UTC leap seconds. GPS times are still easily converted to UTC (or local time) for human consumption.
It would have been really nice had the UNIX designers chosen the TAI timescale instead of UTC as the internal representation of time. (GPS didn't exist back in the 1970s when UNIX was developed). Library routines could easily convert between TAI and UTC as needed for input and display, using configuration files updated every time a new leap second is declared, but you'd get a much cleaner internal representation of time. You wouldn't have the present situation where every timestamp for a past event is effectively moved one second every time there's a leap second.
I wonder if it's too late to make such a change...