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FW: Australian DST abbreviations causing business problems - still
by Olson, Arthur David (NIH/NCI) [E] Jan. 16, 2009

Jan. 16, 2009

I'm forwarding this message from Mick Johnston, who is not on the time zone mailing list. Those of you who are on the list, please direct replies appropriately. --ado -----Original Message----- From: Mick Johnston [mailto:Mick.Johnston@coles.com.au] Sent: Tuesday, August 26, 2008 1:42 To: 'tz(a)elsie.nci.nih.gov' Subject: Australian DST abbreviations causing business problems - still It's well past time the Australian 'Daylight Saving Time' abbreviations were updated to reflect the current terms and usage. Comments posted previously in the 'australasia' file are outdated and wrong and have been causing lots of problems for years. You don't have to take my word for this. Although most of the URLs identified in the file are not official sites and Daylight Saving Time is legislated by state governments, the exemplary abbreviations are displayed at the Australian federal government website at <http://www.australia.gov.au/Time#daylightsaving> as at 26/8/08. Here is the important bit: Quote: Where daylight saving is being observed: * AEST becomes Australian Eastern Daylight Time (AEDT), and clocks are advanced to UTC +11. * ACST becomes Australian Central Daylight Time (ACDT), and clocks are advanced to UTC +10 ½. * AWST becomes Australian Western Daylight Time (AWDT), and clocks are advanced to UTC +9. " Unquote: The abbreviations AEDT, ACDT and AWDT are commonly shortened to EDT, CDT and WDT. Is there really a problem? Yes. I work for a national retail company that makes deliveries across the country. Here is just one example of the sorts of problems we face. Queensland don't have Daylight Saving Time. New South Wales (across the border from Queensland) do have Daylight Saving Time. Due to the fact that the Olsen data uses EST for both 'Eastern Summer Time' (New South Wales) and 'Eastern Standard Time' (Queensland), a delivery from New South Wales to Queensland can have a pickup time of 10.30am EST and a delivery time of 10.00am EST. We like to be efficient but we're not that good. System users only see the EST and get horribly confused. If the problem impacts businesses, then why don't they use their own time zone tables? It's not that simple. It's quite common today to find systems (like ours) that are purchased on an enterprise licence basis from a large international company. It could be difficult to get the company to change the base software product. Also, it's common for software products to run on standard operating systems such as the AIX flavour of Unix, and for the software products to use whatever time zone information is applied by the operating system. Try getting the operating system vendor to change their software and they'll simply tell you it's based on the Olsen updates. Then why hasn't the table been changed already? To answer this question, I need to address some of the comments previously made in the 'australasia' file. The first comment on this subject in the file was made by John Mackin back in 1991: JM:" We in Australia have _never_ referred to DST as `daylight' time. It is called `summer' time." MJ: This comment is more than 17 years old and horribly outdated. I have lived in Australia all my life and have been supporting systems here since well before 1991. Most Australians simply use the term 'Daylight Saving Time'. It's uncommon outside the business environment to use any other term. In business and government, Australians recognized the problems associated with ambiguous abbreviations a long time ago and have generally adopted the 'EDT' form. Various federal government websites (although not official), in an attempt to encourage uniformity, have been displaying the newer abbreviations for some time. See <http://www.bom.gov.au/climate/averages/tables/daysavtm.shtml> <http://www.australia.gov.au/Time#daylightsaving> Paul Eggert wrote an interesting post in 2001 that needs to be addressed. PE: "My own impression is that both "Daylight Time" and "Summer Time" are common and are widely understood, but that "Summer Time" is more popular;" MJ: Based on my day-to-day observations and discussions with people across states, most Australians now don't use the term 'Eastern Summer Time'. PE: "I just used AltaVista advanced search and got the following count of page hits: 1,103 "Eastern Summer Time" AND domain:au 971 "Australian Eastern Summer Time" AND domain:au 613 "Eastern Daylight Time" AND domain:au 127 "Australian Eastern Daylight Time" AND domain:au" MJ: I just googled (26/8/08) similar searches based on an "Australia only" search and my results were: 30,500 - "eastern daylight time" 5,640 - "eastern summer time" PE: "For abbreviations, tools like AltaVista are less useful because of ambiguity. Many hits are not really time zones, unfortunately, and many hits denote US time zones and not Australian ones. But here are the hit counts anyway: 161,304 "EST" and domain:au 25,156 "EDT" and domain:au" MJ: I agree with your comments, which means the figures are totally inaccurate. File Changes: Due to the fact that the file forms part of the JTZU (Java Time Zone Updates) provided by the operating system vendor, I am unable to create and test proposed changes. Also, there are quite a few changes required and I don't want to spend hours making these changes if they're not going to be applied. I ask for your advice on how to proceed with this. I am happy to work with you to produce a complete set of revised rules if you decide to go ahead with this proposal. We will need to change Aus, AW, AS, AT, AV and AN rules and their corresponding zone formats to use the 'E%sT' format. Thanks for your time and assistance Mick Johnston Dept: CGL - IT ES Supply Chain * L4 Bourke St. Melbourne (ILS Support) * (03) 9635 4457 This email and any attachments may contain privileged and confidential information and are intended for the named addressee only. If you have received this e-mail in error, please notify the sender and delete this e-mail immediately. Any confidentiality, privilege or copyright is not waived or lost because this e-mail has been sent to you in error. It is your responsibility to check this e-mail and any attachments for viruses. No warranty is made that this material is free from computer virus or any other defect or error. Any loss/damage incurred by using this material is not the sender's responsibility. The sender's entire liability will be limited to resupplying the material.

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FW: Notes on 'timesub"
by Olson, Arthur David (NIH/NCI) [E] Jan. 15, 2009

Jan. 15, 2009

I'm forwarding this message from John Dlugosz, who is not on the time zone mailing list. Those of you who are on the list, please direct replies appropriately. --ado From: John Dlugosz [mailto:JDlugosz@TradeStation.com] Sent: Thursday, January 15, 2009 12:40 To: tz(a)lecserver.nci.nih.gov Subject: Notes on 'timesub" The implementation of 'timesub' uses quite a bit of complex logic, approximations, and looping to do what can be done with a single expression. The part of the function that digests the number of days into y/m/d fields has been known since before computers as "Julian Day Number" and that can be harnessed directly simply by subtracting a constant for the Epoch base. Here is my version, which is not so digested into my own library that you can't follow the logic: void timezone_t::state::timesub ( const __time64_t t, // input time number const long offset, // added to time, but figures date from original (e.g. like a denormal value) ymd_hms& tmp // output ) const { // more complex than it needs to be! static const int JDayEpoch= Julian_day_number (ymd(EPOCH_YEAR, 1, 1)); int days_in_epoch = t / SECSPERDAY; int rem = t - days_in_epoch * SECSPERDAY; int corr= count_leap_seconds (JDayEpoch, JDayEpoch+days_in_epoch); tmp= Julian_day_number (JDayEpoch+days_in_epoch); tmp.set_normalized (hms(0,0,rem+offset - corr)); } In your code, the part I'm referring to is the middle. First it finds 'corr' for leap seconds, and afterwards it adds the seconds into the h/m/s possibly overflowing into the d/m/y. I have those in callable functions, but the approach is the same. It's just that the middle part, converting a number of seconds into y/m/d, is not as hard as you make it out to be. This is a direct implementation of the published formula, which involves no looping or successive approximations or peeling off each month individually: ymd Julian_day_number (int J) { const int j= J+32044; const int g= j / 146097; const int dg= j % 146097; const int c= (dg / 36524 + 1) * 3 / 4; const int dc= dg - c * 36524; const int b= dc / 1461; const int db= dc % 1461; const int a= (db/365+1) * 3 / 4; const int da= db - a * 365; const int y= g*400 + c*100 + b*4 + a; const int m= (da*5+308) / 153 - 2; const int d= da - (m+4) *153 / 5 + 122; return ymd (y-4800+(m+2)/12, (m+2)%12+1, d+1); } (The comment that it is (still) more complex than it needs to be is because the normalization code in my library can handle that directly, so I can just call existing code.) --John

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Notes on 'timesub"
by John Dlugosz Jan. 15, 2009

Jan. 15, 2009

The implementation of 'timesub' uses quite a bit of complex logic, approximations, and looping to do what can be done with a single expression. The part of the function that digests the number of days into y/m/d fields has been known since before computers as "Julian Day Number" and that can be harnessed directly simply by subtracting a constant for the Epoch base. Here is my version, which is not so digested into my own library that you can't follow the logic: void timezone_t::state::timesub ( const __time64_t t, // input time number const long offset, // added to time, but figures date from original (e.g. like a denormal value) ymd_hms& tmp // output ) const { // more complex than it needs to be! static const int JDayEpoch= Julian_day_number (ymd(EPOCH_YEAR, 1, 1)); int days_in_epoch = t / SECSPERDAY; int rem = t - days_in_epoch * SECSPERDAY; int corr= count_leap_seconds (JDayEpoch, JDayEpoch+days_in_epoch); tmp= Julian_day_number (JDayEpoch+days_in_epoch); tmp.set_normalized (hms(0,0,rem+offset - corr)); } In your code, the part I'm referring to is the middle. First it finds 'corr' for leap seconds, and afterwards it adds the seconds into the h/m/s possibly overflowing into the d/m/y. I have those in callable functions, but the approach is the same. It's just that the middle part, converting a number of seconds into y/m/d, is not as hard as you make it out to be. This is a direct implementation of the published formula, which involves no looping or successive approximations or peeling off each month individually: ymd Julian_day_number (int J) { const int j= J+32044; const int g= j / 146097; const int dg= j % 146097; const int c= (dg / 36524 + 1) * 3 / 4; const int dc= dg - c * 36524; const int b= dc / 1461; const int db= dc % 1461; const int a= (db/365+1) * 3 / 4; const int da= db - a * 365; const int y= g*400 + c*100 + b*4 + a; const int m= (da*5+308) / 153 - 2; const int d= da - (m+4) *153 / 5 + 122; return ymd (y-4800+(m+2)/12, (m+2)%12+1, d+1); } (The comment that it is (still) more complex than it needs to be is because the normalization code in my library can handle that directly, so I can just call existing code.) --John

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FW: timezone code - re-entrancy issue
by Olson, Arthur David (NIH/NCI) [E] Jan. 15, 2009

Jan. 15, 2009

I'm forwarding this message from John Dlugosz, who is not on the time zone mailing list. Those of you who are on the list, please direct replies appropriately. --ado -----Original Message----- From: John Dlugosz [mailto:JDlugosz@TradeStation.com] Sent: Tuesday, January 06, 2009 7:36 To: tz(a)lecserver.nci.nih.gov Subject: timezone code - re-entrancy issue At the bottom of localsub, tzname[tmp->tm_isdst] = &sp->chars[ttisp->tt_abbrind]; I think this is to update the tzname string to the last time zone abbr. actually used in to produce the tm values. It is not re-entrant. This is called even by localtime_r, which may be changing the values even as another thread (who called plain localtime) is reading it. It also changes all the time as the "binary search" is being done by mktime. That violates the "behaves as if never called" rule, and putting it in a subroutine doesn't help there. Am I missing something? --John

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What are tt_ttisstd and tt_ttisgmt for?
by John Dlugosz Jan. 14, 2009

Jan. 14, 2009

I thought I understood the comment in the file structure, ** one (char [4]) total correction after above ** tzh_ttisstdcnt (char)s indexed by type; if TRUE, transition ** time is standard time, if FALSE, ** transition time is wall clock time ** if absent, transition times are ** assumed to be wall clock time ** tzh_ttisgmtcnt (char)s indexed by type; if TRUE, transition ** time is UTC, if FALSE, ** transition time is local time ** if absent, transition times are ** assumed to be local time but, I don't see them being used the logic to search ats, or to adjust the ats values after loading. So if present in the data file they do nothing. In fact, I got rid of the TRUE's in one of the data files, and it did not make the program produce any different results. What am I missing?

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IERS Message No. 141: New IERS Rapid Service/Prediction Center web site
by central_bureau＠iers.org Jan. 14, 2009

Jan. 14, 2009

************************************************************************ IERS Message No. 141 January 14, 2009 ************************************************************************ New IERS Rapid Service/Prediction Center web site Dear Colleagues, We would like to inform you that the IERS Rapid Service/Prediction Center's web site will be moving from http://maia.usno.navy.mil to http://www.usno.navy.mil/USNO/earth-orientation on 15 January 2009. Note that until the changeover date, the new web site can be found at http://199.211.133.90/USNO/earth-orientation. In addition to the change in address, the style of the web site has been changed to bring it into compliance with an institution-wide format. It is expected that attempting to access the old web site should result in a redirect to the new web site. We have been assured that this change in our web presence will in no way impact our e-mail or our ftp capabilities, i.e. ftp maia.usno.navy.mil will not be impacted. We would appreciate hearing any comments you have regarding the new web site. If you notice any unusual behavior, please let us know. Regards, William Wooden Director, IERS Rapid Service/Prediction Center ************************************************************************ IERS Messages are edited and distributed by the IERS Central Bureau. To subscribe or unsubscribe, please write to <central_bureau(a)iers.org>. Archives: http://www.iers.org/iers/publications/messages/ ************************************************************************

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Meaning of 'goforward' flag ?
by John Dlugosz Jan. 13, 2009

Jan. 13, 2009

I think I understand how the ats array is extrapolated to dates beyond its end. The Gregorian calendar repeats every 400 years, so any rules based on weekdays and day of month numbers will have results that repeat. So, if the date is beyond the end of the array, subtract the smallest multiple of 400 years that produces a date that is within the array, and use the ttis entry that points to. This assumes that the last set of rules in force were used to generate at least 400 years of entries in ats. Is that correct? But, the code to set goforward based on the ats array decides TRUE if there exists an entry that is equivalent to the last entry but exactly 400 years earlier. That does not guarantee that the last 400 years was meant to be repeated. I'm guessing that zic fills out a whole cycle of the last set of rules in force and then one more ats entry to serve as a cue for tzload, or that the POSIX string could generate more than one complete cycle (i.e. MAX_TIMES was large enough). But simply setting a flag in the header, or noting that the POSIX string existed and could fill out 400 years, would be clearer and avoid hidden meanings. As it is, zic would have to be careful to avoid letting that cue occur by happenstance. If you don't worry about that happening, why worry about 'goback', which never occurs in the actual data? Any newly minted time zone would inherit the past from the region is split off from, so it never will. --John

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code review issue re t outside of ats array's range
by John Dlugosz Jan. 13, 2009

Jan. 13, 2009

In 'localsub', If t is before the first entry in ats, and goback is not set, then it uses the first non-DST entry in ats. But, if t is after the last entry in ats and goforward is not net, then it uses the last entry in ats, regardless of whether it is a DST or standard time entry. Is that intentional? ... thinking ... time passes ... I think it's an error either way - if the ats table ends with a seasonal time change and it isn't flagged as goforward, it should be an error that the table was declared too small. It stays in DST forever and if it's flagged as DST that means it was supposed to be a temporary adjustment to the Zone definition. --John

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Timezone code question
by John Dlugosz Jan. 13, 2009

Jan. 13, 2009

The zic program goes to the trouble of generating a POSIX string for "the future" that is the last thing in the data file. The library code turns that into two more ttis records. Why not just store two more ttis records in the file in the first place? What does 'ttis' stand for? What about 'ats'?

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Leap Second Data
by John Dlugosz Jan. 13, 2009

Jan. 13, 2009

Why is the leap second data associated with each data file? Shouldn't it be the same everywhere? --John

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