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Re: Dumb questions about GMT offset in tm structure
by seismo!sun!guy March 20, 1987

March 20, 1987

Given that some people want a facility in some system library to manipulate dates prior to 1902, why not: 1) Leave the UNIX time manipulation routines alone, and use them only for what they were intended - dealing with time stamps for system events. 2) Provide a general-purpose time value manipulation package for the benefit of applications that have to deal with arbitrary dates and times. In fact, you may even be able to write the latter package in some language available on lots of machines (C, Fortran, whatever), and decouple it from the system entirely.

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Re: Dumb questions about GMT offset in tm structure
by seismo!nbires!vianet!devine March 19, 1987

March 19, 1987

Someone wrote: > Yes, but nothing in a UNIX system happened in the 19th century. > Non-UNIX systems lacking "time_t" have done quite well dealing with > times; I don't see any need to use "time_t" for every kind of > timestamp any application could possibly want. Mark replied: ! Sorry, but I disagree. UNIX provides some very nice date/time ! manipulation routines, [...]. I had to reinvent this wheel, and ! I swiped code from ctime like crazy. I wound up choosing ISO time ! (char string) as my standard format. While Unix does not need dates before 1970, I agree it should be more flexible. In order to provide a consistent time format for a network of heterogeneous machines that had time epochs != 1/1/70, I too used the ISO format for dates and times. I didn't have to go as far as Mark did because only network programs (that cared) used the new date/time format; existing programs used OS-dependent calls. Pre-epoch dates were a pain... Bob Devine

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Re: Dumb questions about GMT offset in tm structure
by seismo!cbpavo.MIS.OH.ATT.COM!mark March 18, 1987

March 18, 1987

> > Sometimes we care about things that happened in the 19th century > > (birthdates, for example.) > > Yes, but nothing in a UNIX system happened in the 19th century. > Non-UNIX systems lacking "time_t" have done quite well dealing with > times; I don't see any need to use "time_t" for every kind of > timestamp any application could possibly want. Sorry, but I disagree. UNIX provides some very nice date/time manipulation routines, which know about time zones and daylight time, months of the year, leap years, and various other ugly stuff that people don't like to reimplement. An application that has to store a date has a strong incentive to use the existing routines rather than to invent a new format. It would be VERY NICE if the UNIX routines were useful for more than just timestamps on the local system. It is not necessary that time_t be used for this, as long as there is some standard representation that can do it. ctime might be one, ISO time might be one, or struct tm might be one, or it might be something new. I had to reinvent this wheel, and I swiped code from ctime like crazy. I wound up choosing ISO time (char string) as my standard format. My resulting code is highly unportable, because it knows about time_t and two different conventions for time zone, and it has all the daylight rules built into it. Mark

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Re: List of issues
by ado March 18, 1987

March 18, 1987

> > Should time() return an implementation defined time > > representation or should it return elapsed seconds > > since midnight January 1 1970 GMT? > The current POSIX draft already states that it returns the latter; do > we want to change this? No. . .I want to make sure it stays that way. > X3J11 also has "time" and "time_t", although since they're not > defining an OS standard they do not require "time_t" to be an > integral type representing seconds since the epoch. Ideally, I'd like to see both X3J11 and POSIX define time_t as elapsed seconds since midnight January 1 1970 GMT, and see them both define the time function as returning such a value. If this isn't possible, I'd like to see X3J11 define *differently-named* types and functions--tempus_t and tempus, or whatever. My fear is that there are programs out there that "know" what a time_t is that "know" what the "time" function returns, and that will break if things are changed. -- UUCP: ..seismo!elsie!ado ARPA: elsie!ado(a)seismo.ARPA Elsie and Ado are trademarks of Borden, Inc. and Ampex.

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Ballot # 1
by seismo!nbires!vianet!devine March 18, 1987

March 18, 1987

Since this is the first ballot, here are the balloting rules: 1. Send votes by mail to me (uucp address below) 2. If you feel that the offered choices for an issue are not sufficient, send me mail with suggested addition. If enough suggestions (or one whose argument is compelling) a new round of voting on that issue will be done. 3. Vote EARLY and only once (even if you are from Chicago). 4. If a message never got to your mailbox (you can tell by the reception of the next higher ballot) I will send another to you if it might make a difference in the total vote. 5. Results are piggybacked on ballots to reduce the number of messages. 6. Because there are X issues and not X weeks to discuss them, there will be several ballots per week. 7. I will not decide "winning" choices. I will only keep a count. 8. Discussion of each ballot in the mailing list is encouraged. 9. NOTE: Your votes are not the final say on how the Posix document is structured but are intended to provide valuable input. >> How best to forward the results is still unknown -- comments please.<< If you have any issues you want to see included, please send them to me. I am starting out with, what I hope, will be an issue that will not cause too much argument and gnashing of teeth. Bob Devine {nbires, hao, ihnp4!stcvax} !vianet!devine ----------------- This is Ballot # 1 on Posix time-related issues. 1. Fate of external variables "daylight", "timezone", and "tzname[]" a. Don't put in standard and discourage use. b. Don't put in standard and allow implementation-optional use. c. Place in standard as currently defined in SVID. d. Place in standard but with different or expanded definitions. ----------------- CURRENT LIST OF ISSUES 1. Fate of the external variables daylight, timezone, and tzname[] [ undecided ] 2. Use the user's environment variable to define the timezone for that user [ undecided ] 3. Use the user's environment variable to define timezone rules [ undecided ] 4. How user selects a non-default timezone [ undecided ] 5. Allow user to define a new timezone and set of rules [ undecided ] 6. Definition of what struct tm (or struct new_tm) contains. [ undecided ] 7. List of what time functions are needed. [ undecided ] 8. Definition of what time_t holds.-- implementation defined or seconds since some epoch (eg, 1/1/1970). [ undecided ] 9. Drop mktime from standard because of lack of existing art? [ undecided ]

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Re: Dumb questions about GMT offset in tm structure
by seismo!sun!guy March 18, 1987

March 18, 1987

Sometimes we need subsecond precision. Yes, but "time_t"s need not provide subsecond precision; 4.[23]BSD-style "struct timeval" may not be ideal, but they do the job. Sometimes we care about things that happened in the 19th century (birthdates, for example.) Yes, but nothing in a UNIX system happened in the 19th century. Non-UNIX systems lacking "time_t" have done quite well dealing with times; I don't see any need to use "time_t" for every kind of timestamp any application could possibly want. It might be aesthetically "nice" to have the time representation used by the OS be the same that would be used by every conceivable application, but I don't see that it's worth the effort of changing what a "time_t" is. (There are plenty of OSes out there with the same problem; the VMS epoch starts 00:00 - local time, I believe - November 17, 1858.)

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Re: List of issues
by seismo!sun!guy March 18, 1987

March 18, 1987

1. Should time() return an implementation defined time representation or should it return elapsed seconds since midnight January 1 1970 GMT? The current POSIX draft already states that it returns the latter; do we want to change this? If it does not return elapsed seconds, should the name "time" (or the type name "time_t") be changed (so as to noisily break existing code, rather than quietly breaking existing code?) X3J11 also has "time" and "time_t", although since they're not defining an OS standard they do not require "time_t" to be an integral type representing seconds since the epoch.

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Re: northamerica timezones & Saskatchewan
by seismo!nbires!vianet!devine March 17, 1987

March 17, 1987

Darwyn Peachey peachey(a)sask.UUCP writes: > If I am reading your "northamerica" (version 3.1) timezone file correctly, > it appears to be inaccurate concerning the province of Saskatchewan in > Canada. You seem to assume that all of Canada observes the DST rules. > In fact, Saskatchewan is always on standard time and has been for several > years (up to 20, I'd guess). To be more precise, we are always on daylight > time, since we are geographically in the Mountain zone, but we use Central > Standard Time year round! The information I have found on Saskatchewan Daylight Time is this: 1962-1971 Variable (each locality may have done something different) but it seems to be last Sunday in April to last Sunday in October (September in 1960-1) 1972-present? Observed in entire province except in the far-eastern part (that part is on Central Standard time all year) The western part is on the last Sunday in April to last Sunday in October schedule I don't know where the machine 'skorpio' is but I infer that it is in the Eastern part of Saskatchewan. Does anyone have access to an official publication of Canada that describes DST? Does such a publication exist? Bob Devine

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Re: northamerica timezones & Saskatchewan
by Arthur David Olson March 16, 1987

March 16, 1987

> Saskatchewan is. . .always on daylight time, since we are geographically > in the Mountain zone, but we use Central Standard Time year round! > Thus, there is always a four hour time difference between us and Hawaii. . . > Darwyn Peachey peachey(a)sask.UUCP peacheyd(a)sask.BITNET (306) 966-4909 With a machine name like sask, I'll willing to accept your word as authoritative! Is "CST" the right time zone abbreviation to use in your neck of the woods? Is this: Zone Canada/Saskatchewan -6:00 - CST the right line to have in the northamerica file? --ado

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northamerica timezones & Saskatchewan
by seismo!ihnp4!skorpio!peachey March 16, 1987

March 16, 1987

If I am reading your "northamerica" (version 3.1) timezone file correctly, it appears to be inaccurate concerning the province of Saskatchewan in Canada. You seem to assume that all of Canada observes the DST rules. In fact, Saskatchewan is always on standard time and has been for several years (up to 20, I'd guess). To be more precise, we are always on daylight time, since we are geographically in the Mountain zone, but we use Central Standard Time year round! Thus, there is always a four hour time difference between us and Hawaii (whereas the temperature difference varies from -130F to +20F). Darwyn Peachey peachey(a)sask.UUCP peacheyd(a)sask.BITNET (306) 966-4909

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