App Store won't let me download

I'm trying to download games but every time i do i don't get very far. I touch "free" then "install" then it asks my to verify my password then i do. it brings me back to my home screen shows the icon with a "waiting" bar then i get this pop up that says "a secure connection could not be established. please check your date and time settings." ive checked them and nothing is wrong... what does this have to do with my internet. ive never had a problem using my home wifi till today. Ive synced it, restarted it, everything i could possibly do. how can i fix this?