logoalt Hacker News

minkzilla • yesterday at 9:27 PM • 1 reply • view on HN

Author covers how IANA handles Königsberg, it is logically its own timezone.

  An IANA timezone uniquely refers to the set of regions that not only share the same current rules and projected future rules for civil time, but also share the same history of civil time since 1970-01-01 00:00+0. In other words, this definition is more restrictive about which regions can be grouped under a single IANA timezone, because if a given region changed its civil time rules at any point since 1970 in a a way that deviates from the history of civil time for other regions, then that region can't be grouped with the others
I agree that time is a mess. And the 15 minute offsets are insane and I can't fathom why anyone is using them.

Replies

mzs • yesterday at 10:50 PM

zoneinfo does in practice hold the historical info before 1970 when it can do so easily in its framework: https://en.wikipedia.org/wiki/UTC%2B01:24

  % zdump -i Europe/Warsaw | head
  
  TZ="Europe/Warsaw"
  - - +0124 LMT
  1880-01-01 00 +0124 WMT
  1915-08-04 23:36 +01 CET
  1916-05-01 00 +02 CEST 1
  1916-10-01 00 +01 CET
  1917-04-16 03 +02 CEST 1
  1917-09-17 02 +01 CET
  1918-04-15 03 +02 CEST 1
  % zdump -i Europe/Kaliningrad | head -20
  
  TZ="Europe/Kaliningrad"
  - - +0122 LMT
  1893-03-31 23:38 +01 CET
  1916-05-01 00 +02 CEST 1
  1916-10-01 00 +01 CET
  1917-04-16 03 +02 CEST 1
  1917-09-17 02 +01 CET
  1918-04-15 03 +02 CEST 1
  1918-09-16 02 +01 CET
  1940-04-01 03 +02 CEST 1
  1942-11-02 02 +01 CET
  1943-03-29 03 +02 CEST 1
  1943-10-04 02 +01 CET
  1944-04-03 03 +02 CEST 1
  1944-10-02 02 +01 CET
  1945-04-02 03 +02 CEST 1
  1945-04-10 00 +02 EET
  1945-04-29 01 +03 EEST 1
  1945-10-31 23 +02 EET
  %
➕ show 1 reply