I remember my wife looking for a web dev position in early 2015 and at one place they were adamant that 5 years of HTML5 in experience was mandatory.
Wikipedia says:
On 28 October 2014, HTML5 was released as a W3C Recommendation,[32] bringing the specification process to completion.
Edit: I know the spec was a work in progress since 2008 but it's still kind of a ridiculous requirement. To put it in to perspective, my wife's class was the first year that they trained on Html5 instead of 4.