zoneinfo-right; leap seconds
I've incorporated Guy Harris' asctime_r and ctime_r changes, Paul Eggert's data changes, and Paul's Makefile change to create zoneinfo-right and zoneinfo-posix rather than zoneinfo/right and zoneinfo/posix. Before making new tz...gz stuff available, though, a question: might a name more neutral than "zoneinfo-right" be better? (I'm mindful of our past experience with "Pacific-New"; I don't want to unnecessarily tempt folks to replace "zoneinfo" with "zoneinfo-right".) On leap seconds: having a single leap second file would eliminate the ability to have "rolling" leap seconds. (This was provided when, one year, the city of New York announced that the countdown for the dropping of the big ball that marks the beginning of the new year would run "3...2...1...LEAP...Happy New Year!", putting the leap second at midnight local time. The time zone data as distributed reflects internationally agreed leap-second-occurs-at-the-same-instant-everywhere-on-Earth behavior.) --ado
On Tue, 26 May 1998, Olson, Arthur David wrote:
On leap seconds: having a single leap second file would eliminate the ability to have "rolling" leap seconds. (This was provided when, one year, the city of New York announced that the countdown for the dropping of the big ball that marks the beginning of the new year would run "3...2...1...LEAP...Happy New Year!", putting the leap second at midnight local time. The time zone data as distributed reflects internationally agreed leap-second-occurs-at-the-same-instant-everywhere-on-Earth behavior.)
Has anywhere (with a UTC-based time zone) ever _legally_ instituted such a move of a leap second? What Epoch do systems that use leap seconds use? I can't see any accounting in tz for the 1.999918 seconds of changes (frequency offset of 300 parts in 10^10 for two years plus a step adjustment of 0.107758s at the start of 1972) between the standard Epoch and the start of the leap second system, so do they actually use 1972-01-01 00:00:00Z - 730 days? -- Joseph S. Myers jsm28@cam.ac.uk
"Joseph S. Myers" wrote on 1998-05-26 17:01 UTC:
On Tue, 26 May 1998, Olson, Arthur David wrote:
On leap seconds: having a single leap second file would eliminate the ability to have "rolling" leap seconds. (This was provided when, one year, the city of New York announced that the countdown for the dropping of the big ball that marks the beginning of the new year would run "3...2...1...LEAP...Happy New Year!", putting the leap second at midnight local time. The time zone data as distributed reflects internationally agreed leap-second-occurs-at-the-same-instant-everywhere-on-Earth behavior.)
Has anywhere (with a UTC-based time zone) ever _legally_ instituted such a move of a leap second?
There never was such a thing as a rolling leap second. If the city of New York really started to publish their own time scale with a leap second at 04:60Z = 23:60-05, then they would be running 1 s ahead of US/CA Eastern Time from 19:00 to 23:60 of their NY time. This New York counting sounds very much like an intellectual accident of someone who has heard about leap seconds but didn't understand them fully. As far as I know, there is no geographic region that uses an official time scale with leap seconds but is at the same time not defined by one (or two if summer time is used) fixed offsets to UTC. In the GPS age, there is really no point in having non-UTC-based civil time zones. Markus -- Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK email: mkuhn at acm.org, home page: <http://www.cl.cam.ac.uk/~mgk25/>
Olson, Arthur David wrote:
[M]ight a name more neutral than "zoneinfo-right" be better? (I'm mindful of our past experience with "Pacific-New"; I don't want to unnecessarily tempt folks to replace "zoneinfo" with "zoneinfo-right".)
A fine idea! I propose the use of "zoneinfo-iers". The IERS, or International Earth Rotation Service, http://hpiers.obspm.fr/ , is the agency which decides when to insert leap seconds.
From http://hpiers.obspm.fr/iers/bul/bulc/BULLETINC.GUIDE : "The decision to introduce a leap second in UTC to meet this condition [keeping UT1-UTC smaller than 0.9s in absolute value] is the responsability [sic] of the IERS."
On leap seconds: having a single leap second file would eliminate the ability to have "rolling" leap seconds. (This was provided when, one year, the city of New York announced that the countdown for the dropping of the big ball that marks the beginning of the new year would run "3...2...1...LEAP...Happy New Year!", putting the leap second at midnight local time. The time zone data as distributed reflects internationally agreed leap-second-occurs-at-the-same-instant-everywhere-on-Earth behavior.)
I think rolling leap seconds are a dumb idea. Just because somebody in NYC (it wasn't me, honest!) decided to insert a leap second five hours early, doesn't mean that rational people ought to support this behavior. Similarly, the (former?) existence of an L.A. nightclub which celebrates New Year's Eve every night doesn't mean that some zones have years that are 1 day long. -- John Cowan http://www.ccil.org/~cowan cowan@ccil.org You tollerday donsk? N. You tolkatiff scowegian? Nn. You spigotty anglease? Nnn. You phonio saxo? Nnnn. Clear all so! 'Tis a Jute.... (Finnegans Wake 16.5)
Retrying after a delivery failure at NIH (apologies if the message appears twice): Olson, Arthur David wrote:
[M]ight a name more neutral than "zoneinfo-right" be better? (I'm mindful of our past experience with "Pacific-New"; I don't want to unnecessarily tempt folks to replace "zoneinfo" with "zoneinfo-right".)
A fine idea! I propose the use of "zoneinfo-iers". The IERS, or International Earth Rotation Service, http://hpiers.obspm.fr/ , is the agency which decides when to insert leap seconds.
From http://hpiers.obspm.fr/iers/bul/bulc/BULLETINC.GUIDE : "The decision to introduce a leap second in UTC to meet this condition [keeping UT1-UTC smaller than 0.9s in absolute value] is the responsability [sic] of the IERS."
On leap seconds: having a single leap second file would eliminate the ability to have "rolling" leap seconds. (This was provided when, one year, the city of New York announced that the countdown for the dropping of the big ball that marks the beginning of the new year would run "3...2...1...LEAP...Happy New Year!", putting the leap second at midnight local time. The time zone data as distributed reflects internationally agreed leap-second-occurs-at-the-same-instant-everywhere-on-Earth behavior.)
I think rolling leap seconds are a dumb idea. Just because somebody in NYC (it wasn't me, honest!) decided to insert a leap second five hours early, doesn't mean that rational people ought to support this behavior. Similarly, the (former?) existence of an L.A. nightclub which celebrates New Year's Eve every night doesn't mean that some zones have years that are 1 day long. -- John Cowan http://www.ccil.org/~cowan cowan@ccil.org You tollerday donsk? N. You tolkatiff scowegian? Nn. You spigotty anglease? Nnn. You phonio saxo? Nnnn. Clear all so! 'Tis a Jute.... (Finnegans Wake 16.5)
From: "Olson, Arthur David" <OLSONA@dc37a.nci.nih.gov> Date: Tue, 26 May 1998 12:10:43 -0400 might a name more neutral than "zoneinfo-right" be better? One possible alternative is "zoneinfo-leaps". This would be a bit clearer than "-right". (The POSIX.1 limit on name length is 14 chars, alas.) Date: Tue, 26 May 1998 18:01:43 +0100 (BST) From: "Joseph S. Myers" <jsm28@cam.ac.uk> What Epoch do systems that use leap seconds use? In practice, such systems define 1972-01-01 00:00:00Z == (time_t) 63072000, i.e. it's as if there were no leap seconds before 1972. do they actually use 1972-01-01 00:00:00Z - 730 days? Yes.
From: "Olson, Arthur David" <OLSONA@dc37a.nci.nih.gov> Date: Tue, 26 May 1998 12:10:43 -0400
might a name more neutral than "zoneinfo-right" be better?
One possible alternative is "zoneinfo-leaps". This would be a bit clearer than "-right". (The POSIX.1 limit on name length is 14 chars, alas.)
I guess I've left it too long to reply to this now, but perhaps for next time: How about "zoneinfo-lsecs", "zoneinfo-lpsec", or "zoneinfo-lpscs", so that there can be no doubt what kind of "leaps" are being referred to? _______________ Alex LIVINGSTON Macintosh Support IT, Australian Graduate School of Management (AGSM), Uni. of NSW (UNSW) Fax: +61 2 9931-9349 / Phone: +61 2 9931-9264 / Time: UTC + 10 or 11 h.
participants (6)
-
Alex LIVINGSTON -
John Cowan -
Joseph S. Myers -
Markus Kuhn -
Olson, Arthur David -
Paul Eggert