June 2019 - tz - lists.iana.org

[PROPOSED] * NEWS: Mention -b slim briefly.
by Paul Eggert June 14, 2019

June 14, 2019

--- NEWS | 1 + 1 file changed, 1 insertion(+) diff --git a/NEWS b/NEWS index 0e4c688..7aaae11 100644 --- a/NEWS +++ b/NEWS @@ -4,6 +4,7 @@ Unreleased, experimental changes Briefly: Brazil no longer observes DST. + 'zic -b slim' outputs smaller TZif files; please try it out. Palestine's 2019 spring-forward transition was on 03-29, not 03-30. Changes to future timestamps -- 2.21.0

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[PROPOSED 1/3] Tune and simplify addtype
by Paul Eggert June 14, 2019

June 14, 2019

* zic.c (addtype): Avoid the need to call strcmp each time through the loop checking for duplicate zone types. The strcmp is unnecessary if we already have checked for duplicate abbreviations and so can just look at the strings’ offsets. So, look for those duplicates first. --- zic.c | 36 +++++++++++++++++++----------------- 1 file changed, 19 insertions(+), 17 deletions(-) diff --git a/zic.c b/zic.c index 2cd8cc7..3e27a48 100644 --- a/zic.c +++ b/zic.c @@ -2876,16 +2876,28 @@ addtype(zic_t gmtoff, char const *abbr, bool isdst, bool ttisstd, bool ttisgmt) { register int i, j; - /* - ** See if there's already an entry for this zone type. - ** If so, just return its index. - */ - for (i = 0; i < typecnt; ++i) { + if (! (-1L - 2147483647L <= gmtoff && gmtoff <= 2147483647L)) { + error(_("UT offset out of range")); + exit(EXIT_FAILURE); + } + + for (j = 0; j < charcnt; ++j) + if (strcmp(&chars[j], abbr) == 0) + break; + if (j == charcnt) + newabbr(abbr); + else { + /* + ** See if there's already an entry for this zone type. + ** If so, just return its index. + */ + for (i = 0; i < typecnt; i++) { if (gmtoff == gmtoffs[i] && isdst == isdsts[i] && - strcmp(abbr, &chars[abbrinds[i]]) == 0 && + j == abbrinds[i] && ttisstd == ttisstds[i] && ttisgmt == ttisgmts[i]) return i; + } } /* ** There isn't one; add a new one, unless there are already too @@ -2895,22 +2907,12 @@ addtype(zic_t gmtoff, char const *abbr, bool isdst, bool ttisstd, bool ttisgmt) error(_("too many local time types")); exit(EXIT_FAILURE); } - if (! (-1L - 2147483647L <= gmtoff && gmtoff <= 2147483647L)) { - error(_("UT offset out of range")); - exit(EXIT_FAILURE); - } + i = typecnt++; gmtoffs[i] = gmtoff; isdsts[i] = isdst; ttisstds[i] = ttisstd; ttisgmts[i] = ttisgmt; - - for (j = 0; j < charcnt; ++j) - if (strcmp(&chars[j], abbr) == 0) - break; - if (j == charcnt) - newabbr(abbr); abbrinds[i] = j; - ++typecnt; return i; } -- 2.21.0

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UTC calculation for March 12, 3001 [IANA #1143241], [PR 9419866]
by Lasher, Beth June 10, 2019

June 10, 2019

In the year 3001, Daylight Savings time is applied on Sunday March 9, 3001 as expected. (Eastern Standard time). BUT on the following Thursday, March 12, 3001 at 3 am, it seems that another Daylight Savings Time change is applied. After March 12, 3001, the UTC time zone offset for Eastern Daylight Savings Time is 3 hours (not 4) and remains that way until the year 9999. Is this correct? What is the cause of this second time offset change?

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[PROPOSED] Cite US DST legislation
by Paul Eggert June 7, 2019

June 7, 2019

* northamerica: Cite all the US federal DST legislation. (US): Adjust table to match the legislation more closely. This does not affect the TZif output files. --- northamerica | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) diff --git a/northamerica b/northamerica index 65827ec..52898de 100644 --- a/northamerica +++ b/northamerica @@ -93,10 +93,24 @@ # was the first nationwide legal time standard, and apparently # time was just called "Standard Time" or "Daylight Saving Time". -# From Arthur David Olson: -# US Daylight Saving Time ended on the last Sunday of *October* in 1974. -# See, for example, the front page of the Saturday, 1974-10-26 -# and Sunday, 1974-10-27 editions of the Washington Post. +# From Paul Eggert (2019-06-04): +# Here is the legal basis for the US federal rules. +# * Public Law 65-107 (1918-03-19) implemented standard and daylight saving +# time for the first time across the US, springing forward on March's last +# Sunday and falling back on October's last Sunday. +# * Public Law 66-40 (1919-08-20) repealed DST on October 1919's last Sunday. +# * Public Law 77-403 (1942-01-20) started wartime DST on 1942-02-09. +# * Public Law 79-187 (1945-09-25) ended wartime DST on 1945-09-30. +# * Public Law 89-387 (1966-04-13) reinstituted a national standard for DST, +# from April's last Sunday to October's last Sunday, effective 1967. +# * Public Law 93-182 (1973-12-15) moved the 1974 spring-forward to 01-06. +# * Public Law 94-434 (1974-10-05) moved the 1975 spring-forward to +# February's last Sunday. +# * Public Law 99-359 (1986-07-08) moved the spring-forward to April's first +# Sunday. +# * Public Law 109-50 (2005-08-08), effective 2007, moved the spring-forward +# to March's second Sunday and the fall-back to November's first Sunday. +# All transitions are at 02:00 local time. # From Arthur David Olson: # Before the Uniform Time Act of 1966 took effect in 1967, observance of @@ -152,11 +166,11 @@ Rule US 1918 1919 - Mar lastSun 2:00 1:00 D Rule US 1918 1919 - Oct lastSun 2:00 0 S Rule US 1942 only - Feb 9 2:00 1:00 W # War Rule US 1945 only - Aug 14 23:00u 1:00 P # Peace -Rule US 1945 only - Sep lastSun 2:00 0 S +Rule US 1945 only - Sep 30 2:00 0 S Rule US 1967 2006 - Oct lastSun 2:00 0 S Rule US 1967 1973 - Apr lastSun 2:00 1:00 D Rule US 1974 only - Jan 6 2:00 1:00 D -Rule US 1975 only - Feb 23 2:00 1:00 D +Rule US 1975 only - Feb lastSun 2:00 1:00 D Rule US 1976 1986 - Apr lastSun 2:00 1:00 D Rule US 1987 2006 - Apr Sun>=1 2:00 1:00 D Rule US 2007 max - Mar Sun>=8 2:00 1:00 D -- 2.21.0

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tzdb-latest.tar.gz download issue
by Matt Johnson June 4, 2019

June 4, 2019

The lzip file, https://www.iana.org/time-zones/repository/tzdb-latest.tar.lz redirects to https://data.iana.org/time-zones/tzdb-latest.tar.lz and downloads successfully. The gzip file, https://www.iana.org/time-zones/repository/tzdb-latest.tar.gz redirects to https://data.iana.org/time-zones/tzdb-latest.tar.gz and then fails with a 404. They both used to work, not sure what happened. Thanks, Matt

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Extend POSIX TZ to allow transition times outside 00-24 range, permanent DST
by Paul Eggert June 3, 2019

June 3, 2019

I recently proposed extending the POSIX spec for TZ strings. Please see: http://austingroupbugs.net/view.php?id=1252 This proposal is a modest one, as it doesn't specify TZ strings like 'America/Los_Angeles'. Instead it merely specifies the strings generated by zic and stored into TZif files. This includes strings like '<-03>3<-02>,M3.5.0/-2,M10.5.0/-1' which use times of day outside the 00-24 range, and strings like 'EST5EDT,0/0,J365/25' that represent permanent daylight saving time. This extension to POSIX TZ strings has already been specified in Internet RFC 8536 section 3.3.1 <https://tools.ietf.org/html/rfc8536#page-13> and I think it's a good idea to backport the extension to POSIX itself, as this will bless the common practice of taking the last line of a TZif file and using it as a TZ string on small platforms that lack room to store the TZif files. Please feel free to comment at austingroupbugs.net.

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[PROPOSED] Add an outline to tz-link.html
by Paul Eggert June 1, 2019

June 1, 2019

* tz-link.html: Add an outline, so that it’s more like theory.html. --- tz-link.html | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 92 insertions(+), 2 deletions(-) diff --git a/tz-link.html b/tz-link.html index e0d8cc8..85fc001 100644 --- a/tz-link.html +++ b/tz-link.html @@ -18,6 +18,46 @@ histories and planned futures are often recorded only fitfully. Here is a summary of attempts to organize and record relevant data in this area. </p> + <h3>Outline</h3> + <nav> + <ul> + <li>The <code><abbr>tz</abbr></code> database product and process + <ul> + <li><a href="#tzdb">The <code><abbr>tz</abbr></code> database</a></li> + <li><a href="#download">Downloading the <code><abbr>tz</abbr></code> database</a></li> + <li><a href="#changes">Changes to the <code><abbr>tz</abbr></code> database</a></li> + <li><a href="#commentary">Commentary on the <code><abbr>tz</abbr></code> database</a></li> + </ul> + </li> + <li>Uses of the <code><abbr>tz</abbr></code> database + <ul> + <li><a href="#web">Web sites using recent versions of the <code><abbr>tz</abbr></code> database</a></li> + <li><a href="#protocols">Network protocols for <code><abbr>tz</abbr></code> data</a></li> + <li><a href="#compilers">Other <code><abbr>tz</abbr></code> compilers</a></li> + <li><a href="#TZif">Other <abbr>TZif</abbr> readers</a></li> + <li><a href="#software">Other <code><abbr>tz</abbr></code>-based time zone software</a></li> + </ul> + </li> + <li>Related data + <ul> + <li><a href="#other-dbs">Other time zone databases</a></li> + <li><a href="#maps">Maps</a></li> + <li><a href="#boundaries">Time zone boundaries</a></li> + </ul> + </li> + <li>Timekeeping concepts + <ul> + <li><a href="#civil">Civil time concepts and history</a></li> + <li><a href="#national">National histories of legal time</a></li> + <li><a href="#precision">Precision timekeeping</a></li> + <li><a href="#notation">Time notation</a></li> + <li><a href="#see-also">See also</a></li> + </ul> + </li> + </ul> + </nav> + +<section> <h2 id="tzdb">The <code><abbr title="time zone">tz</abbr></code> database</h2> <p> The <a href="https://en.wikipedia.org/wiki/Public_domain">public-domain</a> @@ -88,6 +128,9 @@ Universal Time</a> (<abbr>UTC</abbr>). The database also records when daylight saving time was in use, along with some time zone abbreviations such as <abbr>EST</abbr> for Eastern Standard Time in the <abbr>US</abbr>.</p> +</section> + +<section> <h2 id="download">Downloading the <code><abbr>tz</abbr></code> database</h2> <p> The following <a @@ -148,6 +191,9 @@ specified by <a href="https://tools.ietf.org/html/8536">Internet The code also lets you read a <abbr>TZif</abbr> file and interpret timestamps for that location.</p> +</section> + +<section> <h2 id="changes">Changes to the <code><abbr>tz</abbr></code> database</h2> <p> The <code><abbr>tz</abbr></code> code and data @@ -226,6 +272,9 @@ found in <a href="theory.html">Theory and pragmatics of the tz code and data</a> <a href="https://a0.github.io/a0-tzmigration/">A0 TimeZone Migration</a> displays changes between recent <code><abbr>tzdb</abbr></code> versions. </p> +</section> + +<section> <h2 id="commentary">Commentary on the <code><abbr>tz</abbr></code> database</h2> <ul> <li>The article @@ -239,6 +288,9 @@ href="https://blog.jonudell.net/2009/10/23/a-literary-appreciation-of-the-olsonz literary appreciation of the Olson/Zoneinfo/tz database</a> comments on the database's style.</li> </ul> +</section> + +<section> <h2 id="web">Web sites using recent versions of the <code><abbr>tz</abbr></code> database</h2> <p> @@ -270,6 +322,9 @@ calculates the current time difference between locations.</li> <li><a href="http://www.wx-now.com">Weather Now</a> and <a href="http://www.thetimenow.com">The Time Now</a> list the weather too.</li> </ul> +</section> + +<section> <h2 id="protocols">Network protocols for <code><abbr>tz</abbr></code> data</h2> <ul> <li>The <a href="https://www.ietf.org">Internet Engineering Task Force</a>'s @@ -302,6 +357,9 @@ title="Extensible Markup Language">XML</abbr></a> format, and a variant uses <a href="https://www.json.org"><abbr title="JavaScript Object Notation">JSON</abbr></a> format.</li> </ul> +</section> + +<section> <h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2> <ul> <li><a href="https://sourceforge.net/projects/vzic/">Vzic</a> is a <a @@ -439,6 +497,9 @@ source into text files, along with a runtime that can read those files. Tcl is freely available under a <abbr>BSD</abbr>-style license.</li> </ul> +</section> + +<section> <h2 id="TZif">Other <abbr>TZif</abbr> readers</h2> <ul> <li>The <a @@ -497,6 +558,9 @@ package contains <a href="https://www.haskell.org">Haskell</a> code that parses and uses <abbr>TZif</abbr> data. It is freely available under a <abbr>BSD</abbr>-style license.</li> </ul> +</section> + +<section> <h2 id="software">Other <code><abbr>tz</abbr></code>-based time zone software</h2> <ul> <li><a href="https://foxclocks.org">FoxClocks</a> @@ -554,6 +618,9 @@ a macOS program. Its developers <a href="http://veladg.com/tzoffer.html">offer free licenses</a> to <code><abbr>tz</abbr></code> contributors.</li> </ul> +</section> + +<section> <h2 id="other-dbs">Other time zone databases</h2> <ul> <li><a href="https://www.astro.com/atlas">Time-zone Atlas</a> @@ -582,6 +649,9 @@ Schedules Information Manual</a> of the International Air Transport Association gives current time zone rules for airports served by commercial aviation.</li> </ul> +</section> + +<section> <h2 id="maps">Maps</h2> <ul> <li>The <a href="https://www.cia.gov/index.html">United States Central @@ -609,6 +679,9 @@ much is time wrong around the world?</a> maps the difference between mean solar and standard time, highlighting areas such as western China where the two differ greatly. It's a bit out of date, unfortunately.</li> </ul> +</section> + +<section> <h2 id="boundaries">Time zone boundaries</h2> <p>Geographical boundaries between timezones are available from several <a href="https://en.wikipedia.org/wiki/Geolocation">geolocation</a> @@ -683,6 +756,9 @@ for land and territorial waters only). A captain can change ship's clocks any time after entering a new time zone; midnight changes are common.</li> </ul> +</section> + +<section> <h2 id="civil">Civil time concepts and history</h2> <ul> <li><a href="https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-thr…">A @@ -704,6 +780,9 @@ time zone boundary.</li> <li><a href="http://statoids.com/tconcept.html">Basic Time Zone Concepts</a> discusses terminological issues behind time zones.</li> </ul> +</section> + +<section> <h2 id="national">National histories of legal time</h2> <dl> <dt>Australia</dt> @@ -790,6 +869,9 @@ Navy (SOHMA) publishes an annual <a href="http://www.armada.gub.uy/sohma/index.php/servicios/datos-astronomicos" hreflang="es">almanac (in Spanish)</a>.</dd> </dl> +</section> + +<section> <h2 id="precision">Precision timekeeping</h2> <ul> <li><a @@ -878,6 +960,9 @@ without Leap Seconds</a> gives pointers on this contentious issue, which was active until 2015 and could become active again.</li> </ul> +</section> + +<section> <h2 id="notation">Time notation</h2> <ul> <li>The <a id="CLDR" href="http://cldr.unicode.org">Unicode Common Locale Data @@ -946,18 +1031,23 @@ any future changes to the rules. One should never set local time is nine hours ahead of <abbr>UT</abbr> and the time zone is called "<abbr>GMT</abbr>".</li> </ul> +</section> + +<section> <h2 id="see-also">See also</h2> <ul> <li><a href="theory.html">Theory and pragmatics of the tz code and data</a></li> <li><a href="tz-art.html">Time and the Arts</a></li> </ul> +</section> + +<footer> <hr> -<address> This web page is in the public domain, so clarified as of 2009-05-17 by Arthur David Olson. <br> Please send corrections to this web page to the <a href="mailto:tz@iana.org">time zone mailing list</a>. -</address> +</footer> </body> </html> -- 2.17.1

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