- tz - lists.iana.org

FW: Error in timezone data
by Olson, Arthur David Aug. 28, 1997

Aug. 28, 1997

---------- From: Lee Steakley[SMTP:lee_steakley@eagle1.turner.com] Sent: Wednesday, August 27, 1997 4:37 PM To: tz(a)elsie.nci.nih.gov Subject: Error in timezone data I believe I found an error in the summer-time rules for Uruguay. The latest version of the data (1997g) has the following as the last few lines of the Uruguay rule: Rule Uruguay 1989 only - Mar 12 0:00 0 - Rule Uruguay 1989 only - Oct 29 0:00 1:00 S Rule Uruguay 1990 1992 - Mar Sun>=1 0:00 0 - Rule Uruguay 1990 1991 - Oct Sun>=21 0:00 1:00 S Rule Uruguay 1992 1993 - Oct Sun>=15 0:00 1:00 S Rule Uruguay 1993 only - Feb 28 0:00 0 - I think the intent is to stop observing summer time after 1993 Feb 28. However, the effect is to keep summer time forever after 1993 Oct. I believe the next-to-last line should read: Rule Uruguay 1992 only - Oct Sun>=15 0:00 1:00 S That way, the change to standard time on 1993 Feb 28 is the last rule executed. On a personal note, I just want to thank you for going to all the trouble of compiling this vast repository of time zone information. I couldn't imagine trying to pull all this together myself. Thanks also for supplying it so freely to the Internet community.

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Error in timezone data
by Lee Steakley Aug. 27, 1997

Aug. 27, 1997

I believe I found an error in the summer-time rules for Uruguay. The latest version of the data (1997g) has the following as the last few lines of the Uruguay rule: Rule Uruguay 1989 only - Mar 12 0:00 0 - Rule Uruguay 1989 only - Oct 29 0:00 1:00 S Rule Uruguay 1990 1992 - Mar Sun>=1 0:00 0 - Rule Uruguay 1990 1991 - Oct Sun>=21 0:00 1:00 S Rule Uruguay 1992 1993 - Oct Sun>=15 0:00 1:00 S Rule Uruguay 1993 only - Feb 28 0:00 0 - I think the intent is to stop observing summer time after 1993 Feb 28. However, the effect is to keep summer time forever after 1993 Oct. I believe the next-to-last line should read: Rule Uruguay 1992 only - Oct Sun>=15 0:00 1:00 S That way, the change to standard time on 1993 Feb 28 is the last rule executed. On a personal note, I just want to thank you for going to all the trouble of compiling this vast repository of time zone information. I couldn't imagine trying to pull all this together myself. Thanks also for supplying it so freely to the Internet community.

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RE: bug in mktime() normalization?
by Olson, Arthur David Aug. 25, 1997

Aug. 25, 1997

Below find changes to localtime.c designed to deal with the situation described by Tom Peterson. The challenge we're faced with is that we don't want to prematurely normalize the tm_sec field in a structure passed to "mktime"--the field might contain a value associated with a leap second. The approach taken below is to first do things without normalizing but, if that fails, to do things using normalization. My check indicates that this approach gives the desired behavior in the example program provided by Tom. --ado *** 7.61/localtime.c Mon Aug 25 13:23:24 1997 --- 7.62/localtime.c Mon Aug 25 13:23:25 1997 *************** *** 5,11 **** #ifndef lint #ifndef NOID ! static char elsieid[] = "@(#)localtime.c 7.61"; #endif /* !defined NOID */ #endif /* !defined lint */ --- 5,11 ---- #ifndef lint #ifndef NOID ! static char elsieid[] = "@(#)localtime.c 7.62"; #endif /* !defined NOID */ #endif /* !defined lint */ *************** *** 134,139 **** --- 134,143 ---- void(*funcp) P((const time_t *, long, struct tm*)), long offset, int * okayp)); + static time_t time2sub P((struct tm *tmp, + void(*funcp) P((const time_t *, + long, struct tm*)), + long offset, int * okayp, int do_norm_secs)); static void timesub P((const time_t * timep, long offset, const struct state * sp, struct tm * tmp)); static int tmcomp P((const struct tm * atmp, *************** *** 1276,1286 **** } static time_t ! time2(tmp, funcp, offset, okayp) struct tm * const tmp; void (* const funcp) P((const time_t*, long, struct tm*)); const long offset; int * const okayp; { register const struct state * sp; register int dir; --- 1280,1291 ---- } static time_t ! time2sub(tmp, funcp, offset, okayp, do_norm_secs) struct tm * const tmp; void (* const funcp) P((const time_t*, long, struct tm*)); const long offset; int * const okayp; + const int do_norm_secs; { register const struct state * sp; register int dir; *************** *** 1293,1298 **** --- 1298,1308 ---- *okayp = FALSE; yourtm = *tmp; + if (do_norm_secs) { + if (normalize_overflow(&yourtm.tm_min, &yourtm.tm_sec, + SECSPERMIN)) + return WRONG; + } if (normalize_overflow(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR)) return WRONG; if (normalize_overflow(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY)) *************** *** 1421,1426 **** --- 1431,1454 ---- return t; } + static time_t + time2(tmp, funcp, offset, okayp) + struct tm * const tmp; + void (* const funcp) P((const time_t*, long, struct tm*)); + const long offset; + int * const okayp; + { + time_t t; + + /* + ** First try without normalization of seconds + ** (in case tm_sec contains a value associated with a leap second). + ** If that fails, try with normalization of seconds. + */ + t = time2sub(tmp, funcp, offset, okayp, FALSE); + return *okayp ? t : time2sub(tmp, funcp, offset, okayp, TRUE); + } + static time_t time1(tmp, funcp, offset) struct tm * const tmp;

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Re: bug in mktime() normalization?
by Paul Eggert Aug. 21, 1997

Aug. 21, 1997

Date: Tue, 19 Aug 97 14:13:13 -0400 From: Tom Peterson (USG) <tomp(a)zk3.dec.com> In mktime(), or rather time2(), I noticed that a change was made a while back which removed the following seconds normalization: ! if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0) ! normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN); Instead, these seconds are now saved aside into saved_seconds and only added back in after an appropriate match is found using the remaining normalized data. This was to handle leap seconds properly. On systems that support leap seocnds, it's incorrect to normalize the seconds count first, since you don't know how many seconds there are per minute until you determine which minutes you're talking about. For example, with leap second support, mktime should adjust an input value of ``1997-07-01 00:00:-1'' UTC (i.e. tm_sec == -1) so that it becomes 1997-06-30 23:59:60 UTC, but with the code above, mktime generated 1997-06-30 23:59:59 UTC which is incorrect. Here's what UNIX98 has to say regarding this: >From your quote it appears that UNIX98 says the same thing that the C Standard says, which is to say, not much. The C Standard spec for mktime is terribly ambiguous and you've found one of the ambiguities. The C Standard says that mktime can return -1 if attempted in the ``spring forward gap'', but it doesn't say how mktime should determine whether one is in the gap. Any user program that messes in this area is relying on behavior that is not guaranteed by any standard. For what it's worth, the GNU C library's mktime agrees with the tz mktime on your example, whereas Solaris 2.5.1 and BSD/OS 3.0 have the other reasonable interpretation (i.e. both mktime invocations yield 575002800).

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bug in mktime() normalization?
by Tom Peterson Aug. 19, 1997

Aug. 19, 1997

Hi all, I've been looking over the time zone package and testing various scenerios. In mktime(), or rather time2(), I noticed that a change was made a while back which removed the following seconds normalization: ! if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0) ! normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN); Instead, these seconds are now saved aside into saved_seconds and only added back in after an appropriate match is found using the remaining normalized data. The question I have is whether this could lead to erroneous rejection of certain tm structs. For example: If the values (other than tm_sec) of an incoming tm struct result in no match from time2()'s binary search, such as a time between a dst change, the struct is rejected and the function returns WRONG. However, the value of tm_sec may have been large enough to push the rest of my tm struct into an acceptible range where a match could have occurred. As with other tm struct members, the value of tm_sec before normalization is not restricted to the range specified in <time.h>. Here's what UNIX98 has to say regarding this: > The mktime() function converts the broken-down time, expressed as > local time, in the structure pointed to by timeptr, into a time since > the Epoch value with the same encoding as that of the values returned > by time(). The original values of the tm_wday and tm_yday components > of the structure are ignored, and the original values of the other > components are not restricted to the ranges described in the <time.h> > entry. > > ... > > Upon successful completion, the values of the tm_wday and tm_yday > components of the structure are set appropriately, and the other > components are set to represent the specified time since the Epoch, > but with their values forced to the ranges indicated in the <time.h> > entry; the final value of tm_mday is not set until tm_mon and tm_year > are determined. Here's an example program: #include <stdio.h> #include <time.h> #include <stdlib.h> void display_tm(void); void run_test(); struct tm tm; time_t mktime_returned; #define TZ_value "ABC0DEF,J81,J300" #define TM_year 1988 #define TM_mon 3 #define TM_mday 22 #define TM_hour1 2 #define TM_hour2 4 #define TM_min 0 #define TM_sec1 7200 #define TM_sec2 0 #define TM_wday -1 #define TM_yday -1 #define TM_isdst -1 main() { putenv("TZ=ABC0DEF,J81,J300"); printf("TZ = %s\n\n", getenv("TZ")); /* same time as below, but tm_hour and tm_sec have not yet been * normalized */ tm.tm_year = TM_year - 1900; tm.tm_mon = TM_mon - 1; tm.tm_mday = TM_mday; tm.tm_hour = TM_hour1; /* un-normalized hour */ tm.tm_min = TM_min; tm.tm_sec = TM_sec1; /* un-normalized seconds */ tm.tm_wday = TM_wday; tm.tm_yday = TM_yday; tm.tm_isdst = TM_isdst; run_test(); printf("\n"); /* same time as above, but tm_hour and tm_sec have already been * normalized */ tm.tm_year = TM_year - 1900; tm.tm_mon = TM_mon - 1; tm.tm_mday = TM_mday; tm.tm_hour = TM_hour2; /* pre-normalized hour */ tm.tm_min = TM_min; tm.tm_sec = TM_sec2; /* pre-normalized seconds */ tm.tm_wday = TM_wday; tm.tm_yday = TM_yday; tm.tm_isdst = TM_isdst; run_test(); } void run_test(void) { printf("tm struct set to:\n"); display_tm(); if ((mktime_returned = mktime(&tm)) == (time_t)-1) { (void)puts("mktime returned -1 (-unknown-)"); } else { printf("mktime returned value = %d\n", (int) mktime_returned); } printf("mktime() final tm struct reset to:\n"); display_tm(); } void display_tm(void) { printf("tm_year = %d, tm_mon = %d, tm_mday = %d, tm_hour = %d, \ tm_min = %d, sec = %d,\nwday = %d, yday = %d, isdst = %d\n", tm.tm_year, tm.tm_mon, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, tm.tm_wday, tm.tm_yday, tm.tm_isdst); } output ====== $ a.out TZ = ABC0DEF,J81,J300 tm struct set to: tm_year = 88, tm_mon = 2, tm_mday = 22, tm_hour = 2, tm_min = 0, sec = 7200, wday = -1, yday = -1, isdst = -1 mktime returned -1 (-unknown-) mktime() final tm struct reset to: tm_year = 88, tm_mon = 2, tm_mday = 22, tm_hour = 2, tm_min = 0, sec = 7200, wday = -1, yday = -1, isdst = -1 tm struct set to: tm_year = 88, tm_mon = 2, tm_mday = 22, tm_hour = 4, tm_min = 0, sec = 0, wday = -1, yday = -1, isdst = -1 mktime returned value = 575002800 mktime() final tm struct reset to: tm_year = 88, tm_mon = 2, tm_mday = 22, tm_hour = 4, tm_min = 0, sec = 0, wday = 2, yday = 81, isdst = 1 $ I would very much appreciate any thoughts concerning this matter and any possible solutions. thanks, - Tom ===================================================================== Tom Peterson | DIGITAL UNIX Development Environment Digital Equipment Corporation | Phone:(603)884-7550 110 Spit Brook Road ZKO3-2/W17 | FAX:(603)881-2257 Nashua, NH 03062-2698 | Email: mailto:tomp@zk3.dec.com

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Re: FW: tztab entries (forwarded with permission)
by Dave Kelly Aug. 13, 1997

Aug. 13, 1997

>From : x>eggert(a)twinsun.com To : dkelly(a)lhr-sys.DHL.COM Subject : Re: FW: tztab entries (forwarded with permission) CC : tz(a)elsie.nci.nih.gov Date : 13/08/97 00:46 Hi Paul Thanks for your help on this. > Here's what I think you're asking for. If you're interested only in > times now and in the future, then the Olson database contains too many > names, partly because it goes back to 1970 and thus must track > historical changes, and partly because it insists on at least one name > per country. You want just one distinct name for each time zone > future, regardless of country. Yes, this is exactly what we need. > This script assumes that the only thing that > matters about a time zone is its UTC offset; it ignores the time zone > name (e.g. "EST", "EDT") and whether the time is daylight-saving time. Just to reassure me - I assume that futures with the same UTC offsets but with different daylight savings time change dates are considered to be distinct by the script? Can you offer any guidelines on the allocation of canonical names to these futures? The tztab entry on HP-UX does seem to follow a convention of <zone name><offset><dst zone name>, e.g.: GMT0BST, WET0WETDST, PST8PDT, CST-9:30CDT but there appear to be different variations of these, e.g. for Central Europe I could use CET-2CEST or CET-2CETDST (and that's without considering MEDST, MEST, MESZ, METDST). Also "CST" is used in China/Australia/US. What would you recommend as the most common set? Thanks again for the help Dave Kelly

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FW: tztab entries (forwarded with permission)
by Olson, Arthur David Aug. 13, 1997

Aug. 13, 1997

---------- From: Dave Kelly[SMTP:dkelly@lhr-sys.DHL.COM] Sent: Monday, August 11, 1997 2:30 PM To: ibilling(a)lhr-sys.DHL.COM; ado(a)elsie.nci.nih.gov Subject: tztab entries Hello There I wonder if you might be able to help... We are building a reference database in which one of the attributes of a "site" is the timezone in which the site is located. We decided to use the HP-UX timezone name from the tztab file as a reference to a timezone since it seemed as good as anything else. We have now realised that the entries we have as default in tztab are far from complete. Do you know where we could get hold of a tztab file which has a complete list of entries? We are only interested in modern (future) entries, but we are interested in the whole global set. We do not want to maintain multiple tztab entries for countries which use the same zone - i.e. we want to have a single entry for all the countries which use CET/CEST. I have found the tzcode and tzdata files but these do not link to a particular "name" of a timezone such as GMT0BST or CET-1CEST. It would obviously make sense to use something that already exists. Hope you can help or offer some advice Thank you and regards Dave Kelly DHL Worldwide Express dkelly(a)lhr-sys.dhl.com

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Millennium update: Caroline Islands to be renamed
by Eric Ulevik Aug. 12, 1997

Aug. 12, 1997

>From a story in the Sydney Morning Herald 12 August 1997: * The Government of Kiribati is going to rename the Carolines to Millennium * The Old Royal Observatory in Greenwich says the Millennium arrives first at the Balleny Islands off Antartica - 2h2m before the Carolines Regards, Eric Ulevik

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