On 7 Dec 2014 11:29, "Alois Treindl" <alois@astro.ch> wrote:

Dear Paul

I am looking at the timezone for Mexico City 1950.

There is a special rules for DST 12 Feb - 31 July 1950, which seems to apply only to Mexico City.

I need to find out the definition of the geographic area for which this is valid.

You quote as a source
http://www.cddhcu.gob.mx/bibliot/publica/inveyana/polisoc/horver/
but I cannot access that source.

Do you happen to keep an offline copy of that source information?

Best regards

Alois