[tz] Official definition and origin of the term "Central European Time"

Eliot Lear lear at cisco.com
Sat Oct 24 08:00:06 UTC 2015

Hi Even,

My understanding is that there is no specific European directive that
requires that a country use a particular offset, year round.  However,
whatever the country uses, there *is* a directive that states precisely
when summertime begins and ends:


This is reflected in the EU rules that European entries then generally
make use of in the database.

As far as the timezone database is concerned, code does not reference
the term "Central European Time".  A short name such as "CE%sT" is not
official anything but convenience, and is certainly not unique. 


On 10/23/15 8:52 PM, Even Scharning wrote:
> Is there an official definition of the term "Central European Time"
> (CET), specifically which UTC offset(s) it refers to?
> If there is no official definition, where did the term originate from?
> I asked the information desk at the EU (Europe Direct) to help me find
> links to relevant legislature, but their reply was that term CET is
> "not regulated at a EU level, but internationally".
> All credible sources I have found, say that CET is a constant UTC+1.
> The closest thing I have found to an authoritative document, is the
> German Time Act from 1978. It says: "Legal time is Central European
> Time. It is defined as Coordinated Universal Time plus one hour."
> There is no reference to the origin of this definition, and no
> information of whether anyone other than the Germans agree on this
> definition.
> http://www.cl.cam.ac.uk/~mgk25/time/zeitgesetz.en.html
> On the EU's web pages (for instance
> http://europa.eu/contact/index_en.htm) times are usually given in CET,
> not CEST (Central European Summer Time), even though daylight saving
> time is currently observed. Google gives a few hundred thousand
> results for CET on europa.eu, and numerous of these results are hits
> on dates in the daylight saving time period.
> I think it makes more sense to define CET as alternating between UTC+1
> (standard time) and UTC+2 (when DST is observed). (See
> http://time.is/CET for a more elaborate definition.)
> This is in line with for instance the US time zones Pacific Time and
> Eastern Time, which refer to the time currently observed, whether it
> is standard time or daylight saving time.
> Even Scharning
> Time.is - exact time for any time zone
> http://time.is/

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