[tz] Error in Scandinavian tz data

Anders Rosendahl webfirmaet at gmail.com
Sat Jun 17 18:20:53 UTC 2023


I'm developing an application using the JavaScript Intl API (which is
relying on the IANA tz db) for converting between local time and UTC.

I started receiving error reports from users about wrong calculations
(particularly from Denmark in the 1940's), and I discovered that in some
cases daylight saving time was applied in a way not in accordance to
historical facts.

I investigated the IANA tz database files and I discovered that a change
has happened in version 2022b (in the file "europe"). Compared to the
earlier version (2022a), 4 zones seem to have their rules removed and
instead linked to Europe/Berlin:

Link Europe/Berlin Arctic/Longyearbyen
Link Europe/Berlin Europe/Copenhagen
Link Europe/Berlin Europe/Oslo
Link Europe/Berlin Europe/Stockholm

This, evidently, is not correct, and will result in erroneous results for
these zones.

Best wishes,
Anders Rosendahl
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