Visiting the IEEE website, we can find the details about the IEEE 802.11 standards and amendments displayed on a table: http://grouper.ieee.org/groups/802/11/Reports/802.11_Timelines.htm
In order to put them into perspective, I have displayed them on a timeline. As the new amendments and standards are released, this timeline will be updated.
Feel free to download and use the timeline as much as you want. As always, please feel free to share your feedbacks so we can make it better together.
The process made me realize that the 802.11 standard is 20 years old this year!
Click on image to open the PDF version:
Download the 802.11 standards and amendments timeline (PDF, 0.4 MB)
Note: the timeline only displays the published amendments and standards. This is why you won't find 802.11ax for now!