What was the longest government shutdown? See how long each past shutdown lasted.

A government shutdown is inching from possible to likely as the federal fiscal year ends in just two days. Congress has still not reached a compromise on government spending, and the clock is ticking. If the stalemate is not broken before 12:01 a.m. Oct. 1, the United States will enter its 22nd government shutdown in the last five decades.

A shutdown would impact millions of Americans. Beyond the walls of Congress, a shutdown would ripple through various government-run programs, such as federally funded preschool, federal college grants and loans, food safety inspections and more.

Here's a look at the longest federal government shutdown and a brief history of its precedent in American politics.

What was the longest government shutdown?

The longest government shutdown lasted 35 days. Spanning from Dec. 22, 2018 to Jan. 25, 2019, it is also the most recent federal shutdown in U.S. history.

It was the third federal shutdown to occur during the Trump administration; the first lasted three days in January 2018, and the second lasted only a few hours in February 2018.

The second longest government shutdown occurred during the Clinton administration. It lasted 21 days from Dec. 16, 1995, to Jan. 6, 1996.

What is a government shutdown?

A government shutdown occurs when there is a lapse in funding, according to the Center for American Progress. The federal fiscal year runs from Oct. 1 to Sept. 30. If Congress does not agree on spending and pass a federal budget by Oct. 1, the government is forced to shut down.

During a government shutdown, all federal agencies and services that officials do not deem "essential" must stop working. Essential services include the U.S. Postal Service and Medicare and Social Security services.

"Non-essential" work, however, must pause operations, affecting many federal employees and millions of Americans. A shutdown can mean thousands of federal workers furloughed, government food assistance benefits delayed and national parks closed.

How long have U.S. government shutdowns lasted?

Over the last five decades, there have been 21 federal shutdowns:

• 1976: Under President Gerald Ford. Lasted for 11 days.

• 1977: Under President Jimmy Carter. Lasted 12 days.

• 1977: Under Carter. Lasted eight days.

• 1977: Under Carter. Lasted eight days.

• 1978: Under Carter. Lasted 17 days.

• 1979: Under Carter. Lasted 11 days.

• 1981: Under President Ronald Reagan. Lasted two days.

• 1982: Under Reagan. Lasted one day.

• 1982: Under Reagan. Lasted three days.

• 1983: Under Reagan. Lasted three days.

• 1984: Under Reagan. Lasted two days.

• 1984: Under Reagan. Lasted one day.

• 1986: Under Reagan. Lasted one day.

• 1987: Under Reagan. Lasted one day.

• 1990: Under George H.W. Bush. Lasted four days.

• 1995: Under President Bill Clinton. Lasted five days.

• 1996: Under Clinton. Lasted 21 days.

• 2013: Under President Barack Obama. Lasted 17 days.

• 2018: Under President Donald Trump. Lasted three days.

• 2018: Under Trump. Lasted several hours.

• 2019: Under Trump. Lasted 35 days.

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This article originally appeared on USA TODAY: What is the longest government shutdown? A history of federal gridlock