FYI: This year, the 3rd Saturday of September is at 15 September 2018: worldwide yearly Software Freedom Day ( https://www.softwarefreedomday.org/ ).
In The Netherlands there will be an event hosted by the Nederlandse Linux Gebruikers Groep, see https://nllgg.nl/bijeenkomst/20180915 . More events to be found at https://www.softwarefreedomday.org/map/ . Bye, Joost
