A crucial bug was found in v3.0.1 which caused invalid post dates to go
unnoticed in the build chain until the error that popped up was unhelpful.
v3.0.2 throws errors as you’d expect
when there is a post like
_posts/2016-22-01-future.md or a post has an
invalid date like
date: "tuesday" in their front matter.
This should make the experience of working with Jekyll just a little better.