June 1988 - tz - lists.iana.org

Re: leap seconds
by ado June 9, 1988

June 9, 1988

> After some phone calls to NBS and Naval Observatory, I found out > that there have been 14 leap seconds inserted. > > 1) 1972 Jun 30 23:59:60 # NBS Special Publication #432 > ... > 14) 1987 Dec 31 23:59:60 # Naval Observatory Which, providentially, agrees with the data in the comp.sources.unix posting. Hats off to bww and guy! --ado

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Re: leap seconds
by ncifcrf!decwrl.dec.com!devine%cookie.DEC June 9, 1988

June 9, 1988

> The phase 'my clock is 14 seconds slow' has been used recently and is > one off from the 15 leap seconds listed above or the 17 leap seconds > which would have been added had Bob's statement been correct. After some phone calls to NBS and Naval Observatory, I found out that there have been 14 leap seconds inserted. 1) 1972 Jun 30 23:59:60 # NBS Special Publication #432 2) 1972 Dec 31 23:59:60 # NBS Special Publication #432 3) 1973 Dec 31 23:59:60 # NBS Special Publication #432 4) 1974 Dec 31 23:59:60 # NBS Special Publication #432 5) 1975 Dec 31 23:59:60 # NBS Special Publication #432 6) 1976 Dec 31 23:59:60 # NBS Special Publication #432 7) 1977 Dec 31 23:59:60 # NBS Special Publication #432 8) 1978 Dec 31 23:59:60 # NBS Special Publication #432 9) 1979 Dec 31 23:59:60 # Naval Observatory 10) 1981 Jun 30 23:59:60 # Naval Observatory 11) 1982 Jun 30 23:59:60 # Naval Observatory 12) 1983 Jun 30 23:59:60 # Naval Observatory 13) 1985 Jun 30 23:59:60 # Naval Observatory 14) 1987 Dec 31 23:59:60 # Naval Observatory The earth has been slowing down so there won't be a yearly insertion as there was in the 70s. Next leap second is anticipated to be in added in 1 1/2 or 2 years. Bob [ David Hoerl, could you send me mail directly? I can't reply to you using the address I got -- ...!decwrl.dec!cookie.dec.com!devine ]

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Leap seconds
by Ronald G. Tolley June 6, 1988

June 6, 1988

>> 1973 June 30 23:59:60 >> 1973 June 30 23:59:61 > > Positive leap seconds were inserted in all NBS broadcasts > at the end of June 30, 1972 and December 31, 1972 thru 1978. > > [ All years since 1978 have had leap seconds. Bob] A AP article out of Washington written in about May 1985 states that "that [adding leap seconds] was done twice in 1972 and once every year since except 1980 and 1984." The same article stated that the 1985 leap second would be the last second in June. >From the data which has gone around recently including the comment above, I have constructed the following list of leap seconds: 1) 1972 Jun 30 23:59:60 # NBS Special Publication #432 2) 1972 Dec 31 23:59:60 # NBS Special Publication #432 3) 1973 Dec 31 23:59:60 # NBS Special Publication #432 4) 1974 Dec 31 23:59:60 # NBS Special Publication #432 5) 1975 Dec 31 23:59:60 # NBS Special Publication #432 6) 1976 Dec 31 23:59:60 # NBS Special Publication #432 7) 1977 Dec 31 23:59:60 # NBS Special Publication #432 8) 1978 Dec 31 23:59:60 # NBS Special Publication #432 9) 1979 Dec 31 23:59:60 # June or December? # AP Article no leap second in 1980 10) 1981 Dec 31 23:59:60 # June or December? 11) 1982 Dec 31 23:59:60 # June or December? 12) 1983 Dec 31 23:59:60 # June or December? # AP Article no leap second in 1984 13) 1985 Jun 30 23:59:60 # AP Article 14) 1986 Dec 31 23:59:60 # June or December? 15) 1987 Dec 31 23:59:60 # June or December? Is there a more complete or more correct list available? (All this fuss over a handful of seconds!) The phase 'my clock is 14 seconds slow' has been used recently and is one off from the 15 leap seconds listed above or the 17 leap seconds which would have been added had Bob's statement been correct. Ron Tolley

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leap seconds; [0-60] is ok
by ncifcrf!decwrl.dec.com!devine%cookie.DEC June 2, 1988

June 2, 1988

> When the first leap seconds were added, which I believe were in 1973, > there were two inserted at the same time. Thus a single legal value has > had the seconds denoted as "61". From memory, these two leap seconds > were: > > 1973 June 30 23:59:60 > 1973 June 30 23:59:61 No, only one second is ever added at a time. However, Ron is right about the first year (1972) containing two leap seconds. Below is the relevant section describing how leap seconds are inserted/deleted. Bob Devine [ On a sidenote to time, the Herstmonceux Castle where the Greenwich Observatory is located is for sale. You can buy it for only ~$15M.] From the NBS Special Publication #432 (issued in 1979): When leap second adjustments are necessary to keep the broadcast time signals (UTC) within +/- 0.9 second of the earth-related UT1 time scale, the addition or deletion of exactly 1 second occurs at the end of the UTC month. By international agreement, first preference is given to December 31 or June 30, second preference to March 31 or September 30, and third preference to any other month. When a positive leap second is required -- that is, when UT1 is slow relative to UTC -- an additional second is inserted beginning 23h 59m 60s of the last day of the month and ending at 0h 0m 0s of the first day of the following month. In this case the last minute of the month in which there is a leap second contains 61 seconds. Assuming that unexpected large changes do not occur in the earth's rotation rate in the future, it is likely that positive leap seconds will continue to be needed about once per year. If, however, the earth should speed up significantly at some future time, so that UT1 runs at a _faster_ rate than UTC, then provision is also made for negative leap seconds in the UTC time scale. In this case, exactly one second would be deleted at the end of some UTC month, and the last minute would contain only 59 seconds. Positive leap seconds were inserted in all NBS broadcasts at the end of June 30, 1972 and December 31, 1972 thru 1978. [ All years since 1978 have had leap seconds. Bob]

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Re: Time conversion and second public... [forwarded from rgt@hpfcrg]
by ado June 2, 1988

June 2, 1988

> * The range of seconds has been changed from "[0-59]" to "[0-60]" > throughout, to allow for leap seconds. Whether this is a good > thing or not depends on what you think POSIX wants. When the first leap seconds were added, which I believe were in 1973, there were two inserted at the same time. Thus a single legal value has had the seconds denoted as "61". From memory, these two leap seconds were: 1973 June 30 23:59:60 1973 June 30 23:59:61 All other leap seconds, as I recall, have been added singly so other than the single second noted above "[0-60]" would be sufficient. However if we are to do a complete job, let's handle this "61" too. Ron Tolley

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Time conversion and second public review of draft proposed ANSI C
by ado June 1, 1988

June 1, 1988

I've yet to receive the draft proposed standard that's the subject of the third public review period; I have, though, received "X3J11 Response ot Issues Raised by Miscellaneous Public Comments (Not an official X3J11 document)." Here's what the "Response" has to say on time conversion matters: * The range of seconds has been changed from "[0-59]" to "[0-60]" throughout, to allow for leap seconds. Whether this is a good thing or not depends on what you think POSIX wants. * The Committee declined to change the phrase "time zone name" to "time zone name abbreviation". Some vendors will be surprised when they learn that "strftime" is supposed to fill structures with pointers to strings such as "mountain standard time" (which is a time zone name) rather than to strings such as "MST" (which is a time zone name abbreviation). Reading the Committee's response, I'm inclined to believe that I failed to clearly draw the distinction, and that a clearer explanation, along with a modified suggestion that the phrase be changed to "time zone name or abbreviation," might be more positively received. * The Committee declined to move the contents of footnote 109 into the Standard proper. In my letter to the Committee, I said: Footnote 109 reads Thus, a positive or zero value for tm_isdst causes the mktime function initially to presume that Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value for tm_isdst causes the mktime function to attempt to determine whether Daylight Saving Time is in effect for the specified time. The described behavior of mktime when tm_isdst is negative cannot be deduced from the Standard proper; given Section 4.12.1's words that "The value of tm_isdst is. . .negative if the information is not available," an implementer of mktime could reasonably say "No information about DST is available, so we won't try to account for it." Proposed Change Move the text of footnote 109 into the Standard proper, changing "Thus, a positive. . ." to "A positive. . ." The "Response" indicates that the Committee believes the behavior described in footnote 109 represents the only reasonable interpretation of the standard. Looks as if the vendors will be able to take the easy way out (described above), and as if user's won't be able to rely on the "tm_isdst == -1" mechanism to get DST accounted for. -- "Only external identifiers and macro names described in the Standard as reserved shall be reserved" must go in. This is non-negotiable. ado(a)ncifcrf.gov ADO is a trademark of Ampex.

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time representation
by ncifcrf!decwrl.dec.com!devine%cookie.DEC June 1, 1988

June 1, 1988

Bradley White says: > Just as an aside, UNIX time_t values are not an appropriate representation > of time in a distributed system. An ASCII rendition of UT is much better. To continue the aside: The appropriate ISO standards for representing date and time are: ISO 4031, ISO 3307, and ISO 2014. Send me mail if you want some functions that convert time_t to/from a subset of those ISO standards. Bob Devine

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