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.