Which abbreviation to use for the current observed time in Central Europe?

When I talk to colleagues I want to write “Let’s meet 10am London / 11am Europe”, but I want to use an abbreviation.

I used to write “10am GMT / 11am CET”. But if it were daylight savings time this would be incorrect, and has tripped me up many times, like when I type into Google “10am GMT in CET”.

This website claims that CET in common usage means either so that I am correct to use it:

Warning: Many sources define CET as a constant UTC+1. In common usage however, CET usually refers to the time observed in most of Europe, be it standard time or
daylight saving time.

There was another question on here for US, that said PT is the correct term for the observed time in the Pacific time zone region, compared PST and PDT that depend on the time of year.

However, from http://mm.icann.org/pipermail/tz/2015-October/022798.html:

Generally speaking, CET = UTC+1, and CEST = UTC+2. Though in some contexts, CET may be used to identify the pair. It’s slightly different than the US, as we have the generic term Pacific Time to cover both PST and PDT, but Europe doesn’t have such a generic term.

I am really surprised how difficult it is to find an acronym for the current observed time in a time zone region.

Also, if a time zone is the time in a region at a particular time of year, what is the official term for the geographic region that a time zone applies to?

There seems to be an official standard for an area Europe/Berlin, but what I am looking for is an acronym for a group of areas that respect the same time zone.