The Global HF Weekend is coming up November 2-4, 2018.
The GHFW occurs the 1st weekend in April and the first weekend in November every year. The idea is that it's a set time for listeners and stations to try testing to different parts of the world.
Over the past few years, the high frequencies have not been great for propagation between Europe and North America, but stations have still been able to reach other continents by operating at other times, etc.
For more information visit: http://hobbybroadcasting.blogspot.com/