During his presidential announcement speech, Trump said, “The last quarter, it was just announced, our gross domestic product — a sign of strength, right? But not for us. It was below zero. Who ever heard of this? It’s never below zero.”

While Trump was likely referring to percent change in GDP, that too has been below zero many times in the past.

Business Insider – Donald Trump says GDP is ‘never’ below 0%… except it’s below 0% all the time
Politifact – Donald Trump gets claim about U.S. GDP doubly wrong