Intl is great for formatting dates, but parsing of culture-specific dates (and numbers) can be tricky. I wrote a small library that helps with that - https://github.com/codaxy/intl-io.
I18n parsing is indeed hell. I'm very very reluctant to try to add it to ECMA-402 for that particular reason.
Thank you for writing a user land library for it. It's a thankless task and a very important one and I think such a complex problem deserves a userland solution!
