I think AppBrain listing for the app (search google for the app name and appbrain - or on abbrain.com) - and i think they have a history at the bottom that shows when app was released and their upgrade dates etc. (this info is not available on Google Play it seems). If it is not appbrain then it is one of the other alternative stores (but I think it was appbrain.com).
You can also look at appannie.com - for historical graphs you would have to sign up (for free) - however these usually just show the ratings (as long as it made it to top 500 in it's category). However this does not indicate when the app was released etc.