COLLEGE PARK, Maryland — The federal government has to decide on a budget by midnight on April 28th or the government could shut down on President Trump’s 100th day in office.

Following the failure of the Republican effort to repeal and replace the Affordable Care Act, a government shutdown would be a huge embarrassment for a party that controls both Congress and the White House.

Here are some answers to questions that might be on your mind:

How many times has the government shutdown?

Since 1976, the government has shut down 18 times, as this graphic details, most recently in 2013, during the Obama administration.

It’s difficult to find a clear pattern. The government has shut down when one party controls the White House, Senate and House, like the shutdowns under President Jimmy Carter in the late 1970s. It repeatedly shut down under a divided Congress, as was the case during Obama’s and Ronald Reagan’s time in office. And it has shut down several times when one party controls both the House and Senate and another party controls the White House (Bill Clinton, Gerald Ford and George H.W. Bush).

Carter and congressional Democrats shut down the government for more than a week on four separate occasions in the late 1970s, largely because of disagreements on abortion funding.

What needs to happen to prevent a shutdown this time?

To keep the government operating, Congress needs to pass appropriations bills — either separate bills for each section of the government, or, as has typically happened more recently, a massive bill funding multiple parts of the government.

Some analysts are concerned that controversial items — a border wall, Planned Parenthood funding, a massive amount spent on infrastructure — could delay or block passage.

It’s hard to say if that will happen before the end of April, when a temporary funding measure the government passed in December to keep the government going for four months expires.

Wait, a temporary funding measure?

Yes. A “continuing resolution” funds the government at or near the same level as the previous year. This allows the government to continue to run while continuing debate on future funding levels.

The catch: simply continuing funding from previous years does not always account for new funding needs or address emerging problems.

Department of Defense officials told Congress this week that the Army, for example, will have to postpone 47 new programs and 84 old programs in 2017, according to Federal News Radio.

How often has Congress used continuing resolutions?

Pretty frequently. Congress has passed at least one temporary funding patch every year for 20 straight years; the last year without one was 1997.

And in the past two decades, Congress has failed to pass even one regular appropriations bill in 10 of those years. It used to happen pretty sporadically. But it’s been the norm since 2011, a six-year span with no regular appropriations bills being enacted, only continuing resolutions.

What happens during a shutdown?

Federal workers could be furloughed and federal areas like parks or museums could be closed until funding is voted on. So, if you’re a government employee, mark April 29th on your calendar. You may be able to sleep in.