Aw, man. Don't make me bang my head on the desk.
You can't do this by polling free information from the web! Tourists aren't interested in when the next Linux user group meeting is! You need your own list of events updated from local knowledge. Half the interesting stuff is only advertised by people handing out fliers on the street. That means you need to pay people to gather this information for you, which has the knock on effect that you can't cover the whole world, just the bits of it to which lots of tourists go. Isn't this already obvious to you?