Revealed in a blog post, Ubisoft announced that Anno 1800 is free to play from September 1 to 6 on Ubisoft Connect or Epic Games Store. During this period of time, you'll be able to access the full base game with solo, PvP and co-op modes all available for you to try.
Other than that, if you'd like to continue playing and get hold of more content, the Year 3 Gold Edition or the Year 3 Complete Edition can be purchased with 45% off, time-limited discount.
Check the pre-load, starting and ending time in each region for this free weekend in the image below.