Everything ok with the test cases? Solution is running fine on my local machine with Node v4.1.1 When I submit solution though I get NaN for the first test case, 10/13/1964 - Expected: 7, instead got: NaN. Any ideas for why it's failing?

I think we should offer some helpful libraries / functions / hints if a user clicks on an expansion drop down within the instructions pane under the category tags. This will help people who are completely lost on a kata, discouraging cheating.

Solutions !can not! be unlocked for a kata level > than where you are at now. Only kata lower. Viewing solutions has a cost, of one kata completed successfully.

Allow users to submit links to admins for solutions posted online, than can discipline users who posted. Do not discipline submitters though. Warn, discourage, penalize.

This isn't recursive. You are just spliting the string into an array, then reversing the array, then joining it back up. Not manipulating the string recursively.