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utility creating a dst cache
by Chuck Soper Aug. 1, 2003

Aug. 1, 2003

Hello, I'm writing a utility that uses the tz database. One of the features is to quickly (via a cache saved to disk) display daylight saving times for a given year and tz location. If the tz package is updated then I will need to re-create my dst cache. Is there a way to programmatically determine if the tz package has been updated since the last time I ran my utility? Is there a way to determine if a specific zoneinfo file has been updated? Thanks, Chuck

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Antw: utility creating a dst cache
by WHarms＠bfs.de Aug. 1, 2003

Aug. 1, 2003

hi chuck, the modification time is store in the filesystem, for the more paranoid you can use dnotify() an become informed when ever the dir is used. fast way is to store a checksum e.g. md5 and compare after a notify event. walter - - - - - - - - - - - - - - Originalnachricht - - - - - - - - - - - - - - Von: Chuck Soper <chucks(a)lmi.net> Betreff: utility creating a dst cache Datum: 01.08.03 21:43 Hello, I'm writing a utility that uses the tz database. One of the features is to quickly (via a cache saved to disk) display daylight saving times for a given year and tz location. If the tz package is updated then I will need to re-create my dst cache. Is there a way to programmatically determine if the tz package has been updated since the last time I ran my utility? Is there a way to determine if a specific zoneinfo file has been updated? Thanks, Chuck

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RE: epochs and the Gregorian reform
by Infoman July 30, 2003

July 30, 2003

Adding the date of adoption of the Gregorian reform for a given region to the compiled time zone is of interest to the social studies (history, economics, political science) as well as geographers, environmentalists, trade and shipping historians, genealogists, etc.. The results could/should be packaged as a easily reference and useful document for users of this nature. They in turn might be able to provide inputs also. regards - Jake Knoppers -----Original Message----- From: Andrew Brown [mailto:atatat@atatdot.net] Sent: Tuesday, July 29, 2003 8:25 PM To: Oscar van Vlijmen Cc: TZ-list Subject: Re: epochs and the gregorian reform >> while it's not strictly related, i've often found myself wondering if >> adding the date of the adoption of the gregorian reform for a given >> region to the compiled zone file might be of interest. > >One of the places where information about the Julian -> Gregorian transition >dates are kept is The Calendar FAQ: >http://www.tondering.dk/ that's really neat, and i'll bookmark it. that said, informationally, it's approximately the same as the calendrical calculations book. while useful to know about, it's not really sufficient programmatically, since the data is still in "text" form and not easily accessible to your program. :) thanks again for the link. -- |-----< "CODE WARRIOR" >-----| codewarrior(a)daemon.org * "ah! i see you have the internet twofsonet(a)graffiti.com (Andrew Brown) that goes *ping*!" werdna(a)squooshy.com * "information is power -- share the wealth."

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a correction to the tz database
by Härmel Nestra July 30, 2003

July 30, 2003

Hello, I would like to inform you that your database contains incorrect information about the time observed by the Baltic states Estonia and Latvia. According to your database, we are observing standard time, but actually we are observing daylight saving time currently, so our time is 3 hours in advance w.r.t UTC. The DST start and end dates are the same as in EU. I don't know about Lithuania but, according to http://www.worldtimeserver.com/ , it is also observing DST this year. Cheers, HN

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FW: epochs and the gregorian reform
by Olson, Arthur David (NIH/NCI) July 29, 2003

July 29, 2003

Andrew Brown is not on the time zone mailing list; direct replies appropriately. --ado -----Original Message----- From: Andrew Brown [mailto:atatat@atatdot.net] Sent: Tuesday, July 29, 2003 12:20 AM To: tz(a)lecserver.nci.nih.gov Subject: epochs and the gregorian reform while it's not strictly related, i've often found myself wondering if adding the date of the adoption of the gregorian reform for a given region to the compiled zone file might be of interest. i recently worked over cal(1) in netbsd to remove the places where 1752/09/03 was "hard-coded" as the date of the adoption of the reform, adding in it's place a nice list of dates for various places, and demoted 1752/09/03 to a mere default. as a result, i can ask cal to show me the calendar at the time that italy adopted the reform (1582/10/05), or japan (1872/12/20). note that i did not attempt to handle things like sweden from 1700-1712. it struck me that the tz data base would not be an unreasonable place to store the "local" date at which the gregorian reform took place (modulo the various cantons in switzerland and the parts of germany that were protestant in the 16th century). crazy? -- |-----< "CODE WARRIOR" >-----| codewarrior(a)daemon.org * "ah! i see you have the internet twofsonet(a)graffiti.com (Andrew Brown) that goes *ping*!" werdna(a)squooshy.com * "information is power -- share the wealth."

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epochs and the gregorian reform
by Andrew Brown July 28, 2003

July 28, 2003

while it's not strictly related, i've often found myself wondering if adding the date of the adoption of the gregorian reform for a given region to the compiled zone file might be of interest. i recently worked over cal(1) in netbsd to remove the places where 1752/09/03 was "hard-coded" as the date of the adoption of the reform, adding in it's place a nice list of dates for various places, and demoted 1752/09/03 to a mere default. as a result, i can ask cal to show me the calendar at the time that italy adopted the reform (1582/10/05), or japan (1872/12/20). note that i did not attempt to handle things like sweden from 1700-1712. it struck me that the tz data base would not be an unreasonable place to store the "local" date at which the gregorian reform took place (modulo the various cantons in switzerland and the parts of germany that were protestant in the 16th century). crazy? -- |-----< "CODE WARRIOR" >-----| codewarrior(a)daemon.org * "ah! i see you have the internet twofsonet(a)graffiti.com (Andrew Brown) that goes *ping*!" werdna(a)squooshy.com * "information is power -- share the wealth."

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tzdata version - Re: My confusion with Asia/Aqtau
by Robbin Kawabata July 28, 2003

July 28, 2003

> the statement "I hope that I'm using version 2003a." > indicates that we also need to include the tz version where the change was > added. How about adding a version file in the tzdata database, say _tz_version.txt, that contains something like: :::::::::: _tz_version.txt :::::::::: tzdata 2003a _tz_version.txt could be a text file that is part of the tzdata source tar file. zic could install it to the /usr/lib/zoneinfo/ (or wherever) directory. Then zdump -V (new option) could read the _tz_version.txt file, and print the version as "2003a". An inconsistency is that the files in the /usr/lib/zoneinfo/ directory are zoneinfo files, while _tz_version.txt is not. A user (or script) could try to set TZ=_tz_version.txt even though it is not a valid zoneinfo file. It could help to create a new src directory under zoneinfo, that would contain source files.

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Re: DST in Canada through early 1916
by Paul Eggert July 27, 2003

July 27, 2003

Mark, the interesting news in your extracts from the Toronto Star is that Port Arthur, Ontario (now part of Thunder Bay) was observing DST in 1912. This info isn't in the tz database now. This led me to track down a copy of the 19th edition of William Willett's pamphlet "The Waste of Daylight" (dated March 1914). Willett mentions Moose Jaw, and also mentions Port Arthur and Fort William as observing DST two years before Moose Jaw did. (See ref. below.) Since Moose Jaw observed DST in 1912 (according to the Toronto Star), the Thunder Bay region must have observed it starting in 1910. This is a new record for the earliest recorded observance of daylight-saving time. Thanks very much for bringing this to my attention; I'll include a new tz Rule (called "Thunder") in my next proposed update. Unfortunately we don't know when the Thunder Bay region stopped observing DST, or what DST rules they used. For lack of better info, I'll guess they observed DST through 1917 (since Canada had uniform rules in 1918), and that they used Willett's proposal, namely third Sunday in April at 02:00 to third Sunday in September at 03:00. I imagine the only way to check this guess would be to consult the newspapers printed near Thunder Bay at the time. Probably the best place to do that would be the Lakehead University Library. If anyone on the tz list can check that library I'd appreciate any news about this. Reference: <http://www.pettswoodvillage.co.uk/Daylight_Savings_William_Willett.pdf> I just love the Internet for this stuff! Several years ago, I couldn't find a copy of this pamphlet in the University of California research libraries; now it's on the net in PDF form.

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DST in Canada through early 1916
by Paul Eggert July 27, 2003

July 27, 2003

[Forwarded with permission from Mark Brader.] Date: Sat, 26 Jul 2003 19:18:32 -0400 (EDT) From: msb(a)vex.net (Mark Brader) I spent some time at the Toronto Reference Library today. On May 31 I wrote (to Paul and Tom): > The library now has access to a computerized archive of the Toronto > Star back to its founding; I may do a search on DST sometime, but as > I said, I was there for other reasons today, and I didn't want to take > any more time on this. The archive, called "Pages of the Past", contains a scanned image of every page; you can request a particular date and page, or locate pages of possible interest by full-text searches. The search has four options: "exact phrase", "any of these words", "all of these words", "boolean". However, there doesn't seem to be a way to ask for "any of these exact phrases"; at least, the obvious things to try didn't work. Although any library user can access the archive, it's not available on the WWW; you have to go to the library, and access to their computers may be limited if other people are waiting. In this case other people weren't waiting and I was able to get a couple of hours continuously. But again I was there for another reason -- subway history is more interesting than time zone history, after all -- and I didn't want to spend all my time doing this. I chose to search on the exact phrase "daylight saving" (rather than "daylight savings" or "summer time"), and to search forward from the founding of the paper in 1894 until I got to some interesting stuff. Everything below is in my own words. Dates in parentheses are dates of the newspaper articles rather than the events. The very first hit was on (1908-07-09), a one-paragraph item to the effect that New York financiers were alarmed at the popularity of a DST bill in England. Tea time at 5:00, they said, already subtracts too much from business hours. On 1909-03-12 (-13) E.N. Lewis, MP, introduced a bill calling for DST on a national basis for a 2-month period. This was not taken very seriously by the parliamentarians, but it survived to a second reading on 1909-03-29 (-30), when it was referred to committee. On (1914-01-15) it was reported that Lewis was again preparing to introduce his bill -- this time the Star said it called for the clocks to be turned BACK an hour during the summer months! The first actual adoption of DST in Canada was at the municipal level. As the Star put it (1912-06-07), "While people elsewhere have long been talking of legislation to save daylight, the city of Moose Jaw [Saskatchewan] has acted on its own hook." DST in Moose Jaw began on Saturday, 1912-06-01 (no time mentioned: presumably late evening, as below), and would run until "the end of the summer". The discrepancy between municipal time and railroad time was noted. Orillia, Ontario, adopted DST effective Saturday, 1912-06-22, 22:00; the article mentions that Port Arthur (now part of Thunder Bay, Ontario) as well as Moose Jaw have already done so. In Orillia DST was to run until Saturday, 1912-08-31 (no time mentioned), but it was met with considerable hostility from certain segments of the public, and was revoked after only two weeks -- I copied it as Saturday, 1912-07-07, 22:00, but presumably that should be -07-06. (1912-06-19, -07-12; also letters earlier in June). Kenora, Ontario, was to abandon DST on 1914-06-01 (-05-21). Winnipeg, Manitoba, was noted on (1916-02-29) as having adopted DST. On (1916-05-04) it was noted that there was now little doubt that Britain would follow Holland's example and adopt DST. There were many more hits in 1916, and at this point I stopped searching. Feel free to forward this to tz, or better yet, just the interesting bits; or not to, as you wish. -- Mark Brader, Toronto, msb(a)vex.net "No, no, Oscar, you forget. When you and I are together, we never talk about anything except me." --James MacNeill Whistler "It is true, Jimmy, we were talking about you, but I was thinking of myself." --Oscar Wilde

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FW: better overflow check
by Olson, Arthur David (NIH/NCI) July 25, 2003

July 25, 2003

Ulrich Drepper is on the time zone mailing list, but at a different address than the one below. Direct replies carefully. --ado -----Original Message----- From: Ulrich Drepper [mailto:drepper@redhat.com] Sent: Thursday, July 24, 2003 8:53 PM To: tz(a)lecserver.nci.nih.gov Subject: better overflow check -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The code at the end of zic.c:rpytime has the comment Cheap overflow check. Indeed, cheap. And unfortunately insufficient. If the code is executed on a machine with 64 bit time_t the result differs from that you get on a machine with 32 bit time_t. The following patch does a better job. - --- timezone/zic.c 6 Apr 2002 03:39:57 -0000 1.14 +++ timezone/zic.c 25 Jul 2003 00:48:48 -0000 1.15 @@ -2152,12 +2152,13 @@ } if (dayoff < 0 && !TYPE_SIGNED(time_t)) return min_time; + if (dayoff < min_time / SECSPERDAY) + return min_time; + if (dayoff > max_time / SECSPERDAY) + return max_time; t = (time_t) dayoff * SECSPERDAY; - - /* - - ** Cheap overflow check. - - */ - - if (t / SECSPERDAY != dayoff) - - return (dayoff > 0) ? max_time : min_time; + if (t > 0 && max_time - t < rp->r_tod) + return max_time; return tadd(t, rp->r_tod); } - -- - --------------. ,-. 444 Castro Street Ulrich Drepper \ ,-----------------' \ Mountain View, CA 94041 USA Red Hat `--' drepper at redhat.com `--------------------------- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQE/IH8K2ijCOnn/RHQRAgSOAKCGEBJ9z2ToBRnKeXzLgPDMP4m1EgCfSos7 JcgAEplXNFZy95IqU50gsFM= =mZY1 -----END PGP SIGNATURE-----

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