Nobody Ever Drink Water Again, You Left It Out Overnight And It All Spoiled, All Of It

So, you're at the store. You're in the aisle with the water in it, and once you walk past all the empty shelves because you people keep spending whole entire dollars on bottled water when the stuff that comes out of your tap is perfectly good (fracking victims and West Virginia residents excepted) and costs a tiny fraction of a penny for the same amount oh my God what's wrong with you people, eventually you come across some water someone hasn't bought yet. You look on the bottle, and note that it has an expiration date of about two years from now.

So what happens after those two years? Is that when the water becomes unsafe to drink, because of the plastics leaching in or sitting at room temperature for however long or something else?

No. It's water. It's like all the other water. Guy I never caught the name of, please explain where that expiration date comes from.