The government may run out of money by midnight on Thursday, forcing a shutdown and the furlough of hundreds of thousands of federal employees until a funding deal is reached.

It would be the first government shutdown of President Joe Biden’s term and the earliest shutdown in any administration since shutdowns became a part of the funding process in 1980.

Biden had been in office eight months as of September 20, meaning a government shutdown would come at an extremely early stage in his administration.

While there have been 20 funding gaps lasting at least a day since 1976, just 10 have resulted in federal employees being furloughed, according to the House of Representatives website.

The situation stems from the Budget Act of 1974 and the advice of President Jimmy Carter’s Attorney General Benjamin Civiletti in 1980 and 1981 that said funding gaps required the full or partial shutdown of government agencies.

Though there was a funding gap in September 1976 under then President Gerald Ford, the issue of shutdowns and furloughs was not yet established in U.S. politics. Ford had been president since 1974.

The very first furlough took place in May 1980 during the Carter administration but it only affected employees of the Federal Trade Commission. Carter had been in office for more than three years at that point.

A more serious funding gap took place between November 20 and 23, 1981 under then President Ronald Reagan, who had been in office for 10 months as of November 20. He had vetoed a spending bill that did not include as large a cut in domestic spending as he wanted but funding was later restored by a temporary bill.

The events in November 1981 are generally considered to be the first government shutdown in the sense it is now understood.

Funding gaps continued to be an issue for Reagan throughout his administration and federal employees were furloughed again in 1984 and 1986. There were also other funding gaps that did not see furloughs, however.

The only president to avoid a funding gap since the issue first arose in 1976 was former President George W. Bush, who never oversaw a shutdown or furlough of federal employees.

Federal employees were furloughed twice during former President Donald Trump’s administration from January 19 to January 22, 2018 and again from December 21, 2018 to January 25, 2019. There were also two further funding gaps in 2020 that were resolved through continuing resolutions.

It is still possible for Biden to avoid a government shutdown—at least for now—if Democrats and Republicans can agree on a measure to continue funding the government after Thursday. It remains to be seen if this will happen.