I would possibly aim for starting at something like
10:00am @ GMT-8
Assuming a weekday is better than a weekend, Tuesday, Wednesday, and Thursday are the good days. 10am Thursday in San Francisco is 6pm Thursday in London, 7pm Thursday in Berlin, and 7am Friday in New Zealand.
I would like to invite you to meetup called LambdUp. The meetup will be held on December 6, 2017 in Prague. The program of meetup will be about functional programming where you can meet names like Eric Normand, Claudio Ortolina, Andrea Leopardi and more great speakers. Let’s join us and get to know more about Elixir, Clojure, F# and Elm... More info: https://www.lambdup.io/