Hi! This is a dumb question but when do you think Louis and Harry started dating??
Not a dumb question at all.
I think they started dating during the xfactor. They met in mid July, and by July 23 they were already super into each other, as evidenced by Louis literally jumping into Harry's arms and wrapping his legs around him when 1D got formed.
In August they spent around 2 weeks at Robin's bungalow, and they were for sure together then and all the time after that. If they hadn't kissed/hooked up before the bungalow, then I think they were just flirting with each other, but they certainly got together by August. And the rest is history.
There are piles of receipts, timelines, tweets, videos, pictures and other events that back up this view. This is why I say they fell in love at first sight, because they really really did.
I wouldn't be shocked if someday they said they got together within the first week of knowing each other. But as it stands, I think it's safe to say they started dating/got together within a month of knowing each other.
Here's a quick rundown of how fast they got together with dates.
Here's a xfactor timeline (July, August and September).
Here's a detailed xfactor timeline (thru December).
Here's a receipt that states that Larry started dating in the xfactor (the blurred out name is Olly Murs).
Here's proof Louis got together with Harry during the xfactor. Courtesy of Hannah's (Louis' 1st gf) homophobic brother.
Here's a list of evidence about Larry getting together during xfactor.