# Proposed Europe/Oslo timezone alias change could discard pre-1970 data and break Joda-Time behavior

DevFeed: [Proposed Europe/Oslo timezone alias change could discard pre-1970 data and break Joda-Time behavior](<https://devfeed.tech/articles/big-problems-at-the-timezone-database-22010.md>)

Original publisher: [Read original article](<http://blog.joda.org/2021/09/big-problems-at-timezone-database.html>)

Author: Stephen Colebourne (noreply@blogger.com)

Published: 2021-09-25T00:55:00Z

Content type: opinion

Language: en

Sources: [Stephen Colebourne](<https://devfeed.tech/sources/stephen-colebourne.md>)

Topics: [DateTime](<https://devfeed.tech/topics/datetime.md>), [Programming](<https://devfeed.tech/topics/programming.md>), [systems](<https://devfeed.tech/topics/systems.md>), [Operating system](<https://devfeed.tech/topics/operating-system.md>)

Tags: [blog](<https://devfeed.tech/tags/blog.md>), [jdk](<https://devfeed.tech/tags/jdk.md>), [joda](<https://devfeed.tech/tags/joda.md>), [operating-systems](<https://devfeed.tech/tags/operating-systems.md>), [smartphones](<https://devfeed.tech/tags/smartphones.md>), [systems](<https://devfeed.tech/tags/systems.md>), [timezone](<https://devfeed.tech/tags/timezone.md>)

## AI overview

The article criticizes a proposed change to the IANA timezone database that would make Europe/Oslo an alias of Europe/Berlin because their post-1970 data matches. It argues that this could replace researched pre-1970 Oslo data with Berlin data and cause Joda-Time tests and timezone identifier handling to fail.

## Source excerpt

The last time I wrote about the timezone database on this blog, the database was under threat from a lawsuit. Fortunately that lawsuit went away relatively quickly as the company involved got the message that their action was a big mistake. Unfortunately this time the mess is internal. Paul Eggert is the project lead of the timezone database hosted at IANA, a position referred to as the TZ Coordinator. He is an expert in the field, having been involved in documenting timezone data for decades. Unfortunately, he is currently ignoring all objections to an action only he seems intent on making to solve an invented problem that only he sees as important. The database is the world's principle source of timezone information. The data is included in everything from operating systems to smartphones to programming language development kits such as the JDK. While you may never have heard of it, the sheer pervasiveness of the data makes the potential impact of change or damage pretty huge. The timezone database contains information about how clocks have varies in each region around the world. The mandate of the project is to record this information from 1970 onwards. Of course, computers being what they are, a function that returns the timezone for a given date can be passed in a pre-1970 date as well as a post-1970 one. For this, and reasons of completeness, the timezone database contains pre-1970 data as well as post-1970 data. If you go to your JDK or operating system and ask for the timezone offset for 1920-01-01 for the ID "Europe/Oslo" or "Europe/Berlin" you will get an answer: DateTimeZone oslo = DateTimeZone.forID("Europe/Oslo"); System.out.println(oslo.getOffset(new DateTime(1948, 6, 1, 12, 0))); //prints 3600000 DateTimeZone berlin = DateTimeZone.forID("Europe/Berlin"); System.out.println(berlin.getOffset(new DateTime(1948, 6, 1, 12, 0))); //prints 7200000 The proposed change is to downgrade "Europe/Oslo" to be merely an alias for "Europe/Berlin". The rationale is th