What happened to my sweet little boy?

Within a week, the Little Monkey has gone from the sweetest of little boys to a crazed, screaming banshee!! Over night he decided he no longer zonks out at 7pm and instead is up until 9:30 or 10. He throws everything he sees, and tonight we went to a restaurant and had to get everything boxed up due to his flailing and screaming! Please give me tips on disciplining an 18 month old!