This also seems to affect PHP when using the formatting character 'o', which is PHP's version of the ISO-8601 year number. Using 'Y' instead is returning 2014.
When reading the docs [1] it's pretty obvious which one should be used so I am left wondering why I ended up with 'o' in my code. I suspect I copy-pasted something from some random blog post or whatever. Serves me right. :(