According to python.org, Python 3.6.1 was released at the end of March 2017. But:
pyenv install -l | grep 3\.6\.
Output:
3.6.0a1
3.6.0a3
3.6-dev
If you installed pyenv via pyenv installer:
pyenv update
If you installed pyenv via Homebrew (Mac):
brew upgrade pyenv
If you installed pyenv via Git:
cd $(pyenv root) && git pull