Re: [HACKERS] Time zones - Mailing list pgsql-hackers

Tom Lane <tgl@sss.pgh.pa.us> writes:

> The most recent atlas I have says that eastern Alaska is GMT-9,
> western Alaska and Hawaii are GMT-10, and the westernmost Aleutians
> are GMT-11.  No info about daylight savings habits.  A ten-year-old
> atlas claims that all of mainland Alaska is GMT-9.  They may have
> changed things up there recently ... I think we need a native
> guide ...

...or just Olson.  Here are the relevant bits I find in the zoneinfo
library.  The GMTOFF column is the basic (non-DST) offset, RULES is
"-" if there's no DST, the constant "1:00" for the three week period
of the 1933 Hawaiian DST experiment, and "US" to indicate that DST is
used, and follows the US rules I append at the bottom of the list.  In
this case, the FORMAT column has a "%s" that's replaced by the
relevant letter ("S", "W" or "D") from the LETTERS column of the rule.

So, getting back to what someone (Thomas Lockhart?) said:

> I want to confirm that AHST, Alaska-Hawaii Std Time, should have the
> same value as Australia Eastern Std Time, which is what the
> conversion table claims.

I think not.  AH[SD]T used to cover Hawaii and parts of Alaska, but
nowadays it's just parts of Alaska.  Eastern Australia is another four
hours west, over on the other side of the date line, at +10:00 instead
of -10:00.


# Zone    NAME        GMTOFF    RULES    FORMAT    [UNTIL]
Zone Pacific/Honolulu    -10:31:26 -    LMT    1900 Jan  1 12:00        -10:30    -    HST    1933 Apr 30 2:00
-10:30   1:00    HDT    1933 May 21 2:00        -10:30    US    H%sT    1947 Jun  8 2:00        -10:00    -    HST
 

# Zone    NAME        GMTOFF    RULES    FORMAT    [UNTIL]
Zone America/Juneau     -8:57:41 -    LMT    1900 Aug 20 12:00         -8:00    -    PST    1942         -8:00    US
P%sT   1946         -8:00    -    PST    1969         -8:00    US    P%sT    1983 Oct 30 2:00         -9:00    US
AK%sT
Zone America/Yakutat     -9:18:55 -    LMT    1900 Aug 20 12:00         -9:00    -    YST    1942         -9:00    US
Y%sT    1946         -9:00    -    YST    1969         -9:00    US    Y%sT    1983 Oct 30 2:00         -9:00    US
AK%sT
Zone America/Anchorage     -9:59:36 -    LMT    1900 Aug 20 12:00        -10:00    -    CAT    1942        -10:00    US
  CAT/CAWT 1946        -10:00    -    CAT    1967 Apr        -10:00    -    AHST    1969        -10:00    US    AH%sT
1983 Oct 30 2:00         -9:00    US    AK%sT
 
Zone America/Nome    -11:01:38 -    LMT    1900 Aug 20 12:00        -11:00    -    NST    1942        -11:00    US
N%sT   1946        -11:00    -    NST    1967 Apr        -11:00    -    BST    1969        -11:00    US    B%sT    1983
Oct30 2:00         -9:00    US    AK%sT
 
Zone America/Adak    -11:46:38 -    LMT    1900 Aug 20 12:00        -11:00    -    NST    1942        -11:00    US
N%sT   1946        -11:00    -    NST    1967 Apr        -11:00    -    BST    1969        -11:00    US    B%sT    1983
Oct30 2:00        -10:00    US    HA%sT
 

# Rule    NAME    FROM    TO    TYPE    IN    ON    AT    SAVE    LETTER/S
Rule    US    1918    1919    -    Mar    lastSun    2:00    1:00    W # War
Rule    US    1918    1919    -    Oct    lastSun    2:00    0    S
Rule    US    1942    only    -    Feb    9    2:00    1:00    W # War
Rule    US    1945    only    -    Sep    30    2:00    0    S
Rule    US    1967    max    -    Oct    lastSun    2:00    0    S
Rule    US    1967    1973    -    Apr    lastSun    2:00    1:00    D
Rule    US    1974    only    -    Jan    6    2:00    1:00    D
Rule    US    1975    only    -    Feb    23    2:00    1:00    D
Rule    US    1976    1986    -    Apr    lastSun    2:00    1:00    D
Rule    US    1987    max    -    Apr    Sun>=1    2:00    1:00    D

-tih
-- 
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