October 2007 - tz - lists.iana.org

FW: Detroit/Cleveland time zones
by Olson, Arthur David (NIH/NCI) [E] Oct. 3, 2007

Oct. 3, 2007

I'm forwarding this message from Jeff Prucher, who is not on the time zone mailing list. Those of you who are on the time zone mailing list should direct replies appropriately. --ado -----Original Message----- From: Jeff Prucher [mailto:jeff@metaweb.com] Sent: Thursday, September 27, 2007 8:01 To: tz(a)lecserver.nci.nih.gov Subject: Detroit/Cleveland time zones Here is some support for Garland's assertion that ``Cleveland and Detroit advanced their clocks one hour in 1914.'' (Well, at least the Cleveland part.) This does suggest that parts of Ohio were in the central time zone before then, and not in North America/New York. >From "The Newark (Ohio) Daily Advocate", June 18, 1914, page 4, column 2: Cleveland and several other Ohio cities have recently changed or planned to change their clocks from Central to Eastern standard time. As every clock will be set one hour ahead, that means that there will be one hour more of day-light after supper or dinner, whichever the evening meal is called. >From "The Ogden (Utah) Standard", June 20, 1914, page 4, column 1 : Cleveland is about to change its clocks from central to eastern standard time, in order to make longer the period after working hours until dark. Jeff Prucher

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ahem....
by Alf Salte Oct. 3, 2007

Oct. 3, 2007

Should probably clarify that my comments regarding the code for timezone handling refers to the glibc implementation of timezone handling and glibc implmenetaiton of tzset(). After checking your code I see that your implementation varies from the one in glibc and so my question should probably be directed to glibc rather than at your tz package. Hope this clarifies my earlier comments. My questions are still such that I would like answers to them. How much work would it be to make an implementation that did something along the lines as described in my earlier mail? Looking at your code you appear to have a struct state that appear to contain the data which I described in my timezone_t type. Is that a correct understanding or are their details here that I have misunderstood? Alf

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use of global variables in time data.
by Alf Salte Oct. 3, 2007

Oct. 3, 2007

Now, don't get me wrong. We probably have to live with global variables in association with time for a long time - not the least because of backwards compatibility. However, I do feel that a more "object oriented" approach would be superior and wonder how hard it would be to make a rewrite of parts of the code so that one could provide such an interface. It would be particularly useful for languages like C++ etc but would also be useful for C as C too can handle object oriented type features as is handled in FILE etc. What I mean by object oriented approach here is not full fledged OOP - C is not an OO language. What I mean is simply that you can create an object that represent something and then reference that object to refer to that something later and then destroy it when no longer needed. With this in mind I would like a timezone_t type so that you could do something like: timezone_t * tzNY = tzmake("US/Eastern"); // EDT/EST timezone timezone_t * tzUTC = tzmake("Universal"); // or just mktz("") timezone_t * tzlocal = tzmake(NULL); Then you could do stuff like: struct tm nyTime, gmTime, localTime; time_t now; now = time(); tztime(& nyTime, & now, tzNY); // would do the same as gmtime(). tztime(& gmTime, & now, tzUTC); // would do the same as localtime(). tztime(& localtime, & now, tzlocal): // The last one could also be achieved by: tztime(& localtime, & now, NULL); tzrem(tzNY); tzrem(tzUTC); tzrem(tzlocal); ----------------- The existing approach appear simple enough but the problem is that tzset() has the following deficiencies as I see it: 1. It always only operate through TZ variable - would be nice if there was a version that took the data as string so that tzset() could essentially be implemented by calling that function with getenv("TZ") as argument. 2. It leaves the result in various global variables which are defined around the code. Would be nice if the function instead created a struct and kept all data that is to survive the function call within that struct. 3. For backwards compatibility then tzset() should essentially do the folowing: void tzset(void) { struct timezone_t * tzi = tzmake(getenv("TZ")); // copy data from tzi to various global variables. // timezone, altzone, daylight and tzname etc. // details of this depends on exactly what data // are stored in timezone_t // This could also be placed in a separate function // so user can set these variables based on a // previously generated tzmake() call. tzsettz(tzi); tzrem(tzi); } How much work would it take to do such a rewrite? After browsing the source I find that there are numerous global variables between tzset.c and tzfile.c that are not documented anywhere but still are used such as tz_rules and __use_tzfile just to name two of them. Also, if some applications want to avoid allocation of data one could have a version that took the timezone_t struct on input and filled it in. The problem here is how to handle timezone strings. However, assuming that timezone strings are usually small (3-5 letters max for strings like UTC, CEDT, etc.) one could define that timezone_t has allocated say 8 bytes for each of the strings so that it is fixed size. Then one could: struct timezone_t tzUTC; tzmake(& tzUTC, "Universal"); instead of the tzUTC = tzmake("Universal"); I wrote above. In this case the tzrem() function would not be necessary. Yet again both approaches would be possible where tzmake first malloc() a struct large enough to hold the data and then called the other version to fill in the struct. IN this case tzrem would still be needed and you would need two different versions of tzmake(). For example: timezone_t * tzcreate(getenv("TZ")); which was implemented as: timezone_t * tzcreate(const char * tzid) { timezone_t * res = malloc(sizeof(timezone_t)); if (res == NULL) return NULL; tzmake(res,tzid); return res; } Finally, and not really related to the above. I am trying at the moment to read and understand the code. I notice that the tzfile is opened with "rc" mode. I am not sure exactly what the "c" letter there indicates. It says something about prohibiting cancelattion but I am not exactly sure what that means in practice. Is it that if user interrupts the process while in the middle of say reading the file the interrupt will be waiting until the file is closed or what? Alf

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Timezone Options for DHCP
by johnny.walker＠ubs.com Oct. 3, 2007

Oct. 3, 2007

I found a non-functional link on http://www.twinsun.com/tz/tz-link.htm A Timezone Option for DHCP <ftp://ftp.rfc-editor.org/internet-drafts/draft-ietf-dhc-timezone-option -04.txt> proposes a DHCP <http://www.dhcp.org/> option for a server to configure a client's time zone and daylight saving settings automatically "Timezone Options for DHCP" is no longer a draft but a RFC (http://www.ietf.org/rfc/rfc4833.txt) All the best Johnny

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DST extended to November in Syria
by Steffen Thorsen Oct. 3, 2007

Oct. 3, 2007

It seems that Syria was not leaving daylight saving time on 2007-10-01, since it is in the middle of the holy Ramadan month. I have tried to find some info regarding the change, and found the following text in a newspaper (in Arabic): http://www.alwatan.sy/dindex.php?idn=18418 I cannot find that the exact date is there, but 2007-11-01 could be a likely date. Since 2008-10-01 also is in Ramadan (the last date of the month, probably), it is likely that also next year's end date is changed. Google's automated translation of the mentioned URL says: Government set to start with the beginning of winter time in November next unusually where the timing was unusual beginning with the month of October. The postponement of this year due to believe that the holy month of Ramadan and Eid, which ends with the middle of next month, so there is no irregularities in the fasting hours of magic and breakfast with changing times has been postponed to next month.

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Brazil's Time
by Haroldo Macedo Oct. 3, 2007

Oct. 3, 2007

Hello, I've noticed that the Brazil`s daylight saving time isn't updated in your site. It has been officially defined on Sept-26th, and starts on 14-oct-2007 and ends on 17-feb-2008. Below is the link to the Brazilian senate. http://www6.senado.gov.br/legislacao/ListaTextoIntegral.action?id=235121 Attn, -- Haroldo R. J. de Macêdo

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tzcode2007h.tar.gz and tzdata2007h.tar.gz
by Olson, Arthur David (NIH/NCI) [E] Oct. 2, 2007

Oct. 2, 2007

The files... ftp://elsie.nci.nih.gov/pub/tzcode2007h.tar.gz ...and... ftp://elsie.nci.nih.gov/pub/tzdata2007h.tar.gz ...are now available; these reflect the changes circulated last week by Paul Eggert on the time zone mailing list, as well as an updated link to the ICU project in tz-link.htm. --ado

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Brazil summer time 2007/2008
by Marcus Alves Grando Oct. 1, 2007

Oct. 1, 2007

Hi, Like another years, Brazil change summer time for this year. Can you update zoneinfo and release ASAP for inclusion in many distributions? Patch attached. Regards -- Marcus Alves Grando marcus(at)sbh.eng.br | Personal mnag(at)FreeBSD.org | FreeBSD.org

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