done - but clearly did this the long way round
i would be be happy to walk you through my scary code. It really is just a big OR statement to search for the different patterns.
Let me me know if you're interested.
Thank you @MarqueeCrew - walking through it, the OR logic makes sense - the part that I wouldn't have come to on my own steam is the way that it seems that you've replaced the outer part of the string, rather than the pattern-matched date (it seems kinda like saying "this is how you recognize an apple seed - now throw away the rest") :-). it's not an intuitive pattern, but makes sense once you see it.
It would be good to make contact, even if just to extend the network of like-minded folk - not sure how to PM you on the Alteryx infra, but I've sent you a ping on LinkedIn and Google+
Many thanks for your kind offer @MarqueeCrew
I don't know why my attachments are opening in html and not Alteryx.