VMworld US 2017:
Mandalay Bay Convention Center in Las Vegas
August 27 - August 31
Fira Gran Via in Barcelona
September 11 - September 14*
* Please note that the VMworld Europe event is about a month earlier compared to the event dates of previous years. So if you already put a blocker in your calendar, make sure to update this ASAP!
I don't have any information why VMworld has advanced the Europe event, but now the event is closer to the US event and the chances are that you can still enjoy real summer days in Spain are a bit higher.