The Bug:
There is a mineshaft implementation date error in a Deep Dives article: Building Blocks: Mineshaft.

Steps to Reproduce:

1. Open https://www.minecraft.net/en-us/article/mineshaft
2. While you are in the article, look at this part of text in the article. The error is in red text:   

   The first mineshafts were discovered following the release of the Adventure Update in June 2011. They're easy to recognise - a dense network of 3x3 tunnels, lined with oak wood and railways, often covered in cobwebs. 

Observed Results:

There is a date error in the article. The Adventure Update was not released yet when it was June 2011.

Expected Results:

The article should show that Mineshafts were implemented in September 2011, when Java Edition was still in the Beta development stage.