It takes a bit of digging to get the info. In the Buff article it states it starts on with Tues reset on the 19th.
Beginning this week with each region’s local weekly reset, World of Warcraft* players level 10-59 will gain an experience buff called “Winds of Wisdom,” which will increase experience gains by 50%!
Don’t delay. The winds will shift once more with the start of Shadowlands Season 4, and the experience buff will no longer be available.
Then it ends with the start of Season 4. So I went to the pinned post about Season 3 ending which usually tells us when 4 starts. Shadowlands Season 3 Ending Soon
Season 4 will begin with the weekly reset the week of August 2.
It is NOT obvious at all so don’t feel bad you missed the info!
My take on this is that I am rather pleased. I got the Allied race requirements done a few months ago but had not really focused on leveling the alts for Herritage Armor. Got the Void Elf done yesterday. Kul Tiran druid will be next I think. Then adoreable Vulpera!