[tz] Request RE: academic research question re: TZ database

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Wed Jan 8 20:05:45 UTC 2020


On 2020-01-08 12:49, Andrew Lyon wrote:
> I am a clinical biochemist and not well versed in handling the TZ database. I am
> investigating a software problem related to hospital patient data management
> that appears to be triggered when the software encounters a patient record with
> a date-of-birth that coincides with a historic daylight saving time Spring
> transition date.  Through this investigation I have learned many details about
> the history of daylight saving time, but I often question the reliability of
> sources of information.  It appears that many use the tz database as a source of
> truth. 
> 
> I am seeking assistance to query the tz database to determine the entries in the
> database for Area /Location    America/Regina to determine the (1) daylight
> saving time Spring transition date and  (2) daylight saving time Spring
> transition hour from 1900 to 1966. 
> I understand there were 10 years between 1930 and 1941 when the hour of Spring
> daylight saving transition was 0000 (midnight)  to 0100.  I would like to
> confirm these entries are in the tz database.   I have numerous references that
> daylight saving time was also observed in America/Regina  during world war ONE (
> 1914-1918) and I am uncertain if those entries are in the tz database or the
> hour of those transitions. 
> 
> I am uncertain if it is appropriate to ask for this type of assistance on this
> discussion group. 

Attached is the output from zdump -V America/Regina that shows the current
(2019c) tz data for America/Regina.

Problems are often that tz data is not up to date, or data has been converted
using some older data for storage, and is now being converted using newer data
for display, or is using something internal to the database which may have any
of those problems.

Systems that do not use tz data, like older proprietary systems and Windows, may
assume the current year's rules applied to every year, or not handle rules at
all, and only assume local time, so there may be no accurate way of
standardizing any historical entries.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

This email may be disturbing to some readers as it contains
too much technical detail. Reader discretion is advised.
-------------- next part --------------
America/Regina  Fri Sep  1 06:58:35 1905 UT = Thu Aug 31 23:59:59 1905 LMT isdst=0 gmtoff=-25116
America/Regina  Fri Sep  1 06:58:36 1905 UT = Thu Aug 31 23:58:36 1905 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 14 08:59:59 1918 UT = Sun Apr 14 01:59:59 1918 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 14 09:00:00 1918 UT = Sun Apr 14 03:00:00 1918 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 27 07:59:59 1918 UT = Sun Oct 27 01:59:59 1918 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 27 08:00:00 1918 UT = Sun Oct 27 01:00:00 1918 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  4 06:59:59 1930 UT = Sat May  3 23:59:59 1930 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  4 07:00:00 1930 UT = Sun May  4 01:00:00 1930 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  5 05:59:59 1930 UT = Sat Oct  4 23:59:59 1930 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  5 06:00:00 1930 UT = Sat Oct  4 23:00:00 1930 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  3 06:59:59 1931 UT = Sat May  2 23:59:59 1931 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  3 07:00:00 1931 UT = Sun May  3 01:00:00 1931 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  4 05:59:59 1931 UT = Sat Oct  3 23:59:59 1931 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  4 06:00:00 1931 UT = Sat Oct  3 23:00:00 1931 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  1 06:59:59 1932 UT = Sat Apr 30 23:59:59 1932 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  1 07:00:00 1932 UT = Sun May  1 01:00:00 1932 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  2 05:59:59 1932 UT = Sat Oct  1 23:59:59 1932 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  2 06:00:00 1932 UT = Sat Oct  1 23:00:00 1932 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  7 06:59:59 1933 UT = Sat May  6 23:59:59 1933 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  7 07:00:00 1933 UT = Sun May  7 01:00:00 1933 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  1 05:59:59 1933 UT = Sat Sep 30 23:59:59 1933 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  1 06:00:00 1933 UT = Sat Sep 30 23:00:00 1933 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  6 06:59:59 1934 UT = Sat May  5 23:59:59 1934 MST isdst=0 gmtoff=-25200
America/Regina  Sun May  6 07:00:00 1934 UT = Sun May  6 01:00:00 1934 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  7 05:59:59 1934 UT = Sat Oct  6 23:59:59 1934 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  7 06:00:00 1934 UT = Sat Oct  6 23:00:00 1934 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 11 06:59:59 1937 UT = Sat Apr 10 23:59:59 1937 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 11 07:00:00 1937 UT = Sun Apr 11 01:00:00 1937 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 10 05:59:59 1937 UT = Sat Oct  9 23:59:59 1937 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 10 06:00:00 1937 UT = Sat Oct  9 23:00:00 1937 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 10 06:59:59 1938 UT = Sat Apr  9 23:59:59 1938 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 10 07:00:00 1938 UT = Sun Apr 10 01:00:00 1938 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  2 05:59:59 1938 UT = Sat Oct  1 23:59:59 1938 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  2 06:00:00 1938 UT = Sat Oct  1 23:00:00 1938 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr  9 06:59:59 1939 UT = Sat Apr  8 23:59:59 1939 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr  9 07:00:00 1939 UT = Sun Apr  9 01:00:00 1939 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  8 05:59:59 1939 UT = Sat Oct  7 23:59:59 1939 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct  8 06:00:00 1939 UT = Sat Oct  7 23:00:00 1939 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 14 06:59:59 1940 UT = Sat Apr 13 23:59:59 1940 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 14 07:00:00 1940 UT = Sun Apr 14 01:00:00 1940 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 13 05:59:59 1940 UT = Sat Oct 12 23:59:59 1940 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 13 06:00:00 1940 UT = Sat Oct 12 23:00:00 1940 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 13 06:59:59 1941 UT = Sat Apr 12 23:59:59 1941 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 13 07:00:00 1941 UT = Sun Apr 13 01:00:00 1941 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 12 05:59:59 1941 UT = Sat Oct 11 23:59:59 1941 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 12 06:00:00 1941 UT = Sat Oct 11 23:00:00 1941 MST isdst=0 gmtoff=-25200
America/Regina  Mon Feb  9 08:59:59 1942 UT = Mon Feb  9 01:59:59 1942 MST isdst=0 gmtoff=-25200
America/Regina  Mon Feb  9 09:00:00 1942 UT = Mon Feb  9 03:00:00 1942 MWT isdst=1 gmtoff=-21600
America/Regina  Tue Aug 14 22:59:59 1945 UT = Tue Aug 14 16:59:59 1945 MWT isdst=1 gmtoff=-21600
America/Regina  Tue Aug 14 23:00:00 1945 UT = Tue Aug 14 17:00:00 1945 MPT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 30 07:59:59 1945 UT = Sun Sep 30 01:59:59 1945 MPT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 30 08:00:00 1945 UT = Sun Sep 30 01:00:00 1945 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 14 08:59:59 1946 UT = Sun Apr 14 01:59:59 1946 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 14 09:00:00 1946 UT = Sun Apr 14 03:00:00 1946 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 13 07:59:59 1946 UT = Sun Oct 13 01:59:59 1946 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 13 08:00:00 1946 UT = Sun Oct 13 01:00:00 1946 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 27 08:59:59 1947 UT = Sun Apr 27 01:59:59 1947 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 27 09:00:00 1947 UT = Sun Apr 27 03:00:00 1947 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 28 07:59:59 1947 UT = Sun Sep 28 01:59:59 1947 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 28 08:00:00 1947 UT = Sun Sep 28 01:00:00 1947 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 25 08:59:59 1948 UT = Sun Apr 25 01:59:59 1948 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 25 09:00:00 1948 UT = Sun Apr 25 03:00:00 1948 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 26 07:59:59 1948 UT = Sun Sep 26 01:59:59 1948 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 26 08:00:00 1948 UT = Sun Sep 26 01:00:00 1948 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 24 08:59:59 1949 UT = Sun Apr 24 01:59:59 1949 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 24 09:00:00 1949 UT = Sun Apr 24 03:00:00 1949 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 25 07:59:59 1949 UT = Sun Sep 25 01:59:59 1949 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 25 08:00:00 1949 UT = Sun Sep 25 01:00:00 1949 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 30 08:59:59 1950 UT = Sun Apr 30 01:59:59 1950 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 30 09:00:00 1950 UT = Sun Apr 30 03:00:00 1950 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 24 07:59:59 1950 UT = Sun Sep 24 01:59:59 1950 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 24 08:00:00 1950 UT = Sun Sep 24 01:00:00 1950 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 29 08:59:59 1951 UT = Sun Apr 29 01:59:59 1951 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 29 09:00:00 1951 UT = Sun Apr 29 03:00:00 1951 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 30 07:59:59 1951 UT = Sun Sep 30 01:59:59 1951 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 30 08:00:00 1951 UT = Sun Sep 30 01:00:00 1951 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 27 08:59:59 1952 UT = Sun Apr 27 01:59:59 1952 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 27 09:00:00 1952 UT = Sun Apr 27 03:00:00 1952 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 28 07:59:59 1952 UT = Sun Sep 28 01:59:59 1952 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 28 08:00:00 1952 UT = Sun Sep 28 01:00:00 1952 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 26 08:59:59 1953 UT = Sun Apr 26 01:59:59 1953 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 26 09:00:00 1953 UT = Sun Apr 26 03:00:00 1953 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 27 07:59:59 1953 UT = Sun Sep 27 01:59:59 1953 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 27 08:00:00 1953 UT = Sun Sep 27 01:00:00 1953 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 25 08:59:59 1954 UT = Sun Apr 25 01:59:59 1954 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 25 09:00:00 1954 UT = Sun Apr 25 03:00:00 1954 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 26 07:59:59 1954 UT = Sun Sep 26 01:59:59 1954 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 26 08:00:00 1954 UT = Sun Sep 26 01:00:00 1954 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 24 08:59:59 1955 UT = Sun Apr 24 01:59:59 1955 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 24 09:00:00 1955 UT = Sun Apr 24 03:00:00 1955 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 25 07:59:59 1955 UT = Sun Sep 25 01:59:59 1955 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 25 08:00:00 1955 UT = Sun Sep 25 01:00:00 1955 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 29 08:59:59 1956 UT = Sun Apr 29 01:59:59 1956 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 29 09:00:00 1956 UT = Sun Apr 29 03:00:00 1956 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 30 07:59:59 1956 UT = Sun Sep 30 01:59:59 1956 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 30 08:00:00 1956 UT = Sun Sep 30 01:00:00 1956 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 28 08:59:59 1957 UT = Sun Apr 28 01:59:59 1957 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 28 09:00:00 1957 UT = Sun Apr 28 03:00:00 1957 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 29 07:59:59 1957 UT = Sun Sep 29 01:59:59 1957 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Sep 29 08:00:00 1957 UT = Sun Sep 29 01:00:00 1957 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 26 08:59:59 1959 UT = Sun Apr 26 01:59:59 1959 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 26 09:00:00 1959 UT = Sun Apr 26 03:00:00 1959 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 25 07:59:59 1959 UT = Sun Oct 25 01:59:59 1959 MDT isdst=1 gmtoff=-21600
America/Regina  Sun Oct 25 08:00:00 1959 UT = Sun Oct 25 01:00:00 1959 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 24 08:59:59 1960 UT = Sun Apr 24 01:59:59 1960 MST isdst=0 gmtoff=-25200
America/Regina  Sun Apr 24 09:00:00 1960 UT = Sun Apr 24 03:00:00 1960 CST isdst=0 gmtoff=-21600


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