(CNN) Government shutdowns aren't that rare anymore. They've happened many times over the past four decades, stretching back to the Carter administration.

That begs the question: what was the longest shutdown in US history?

That would be the 21-day clash between President Bill Clinton and the GOP Congress that stretched from December 1995 to January 1996.

It lasted three weeks

Congressional Republicans clashed with Clinton, a Democrat, over federal spending. The Republicans refused to OK a spending bill because they wanted the Democrats and the White House to, among other things, agree to deep cuts to Medicare and Medicaid.