Friday was payday for federal workers.

But 800,000 workers received $0 because of the government shutdown.

These workers will not be paid for the duration of the shutdown, but Congress passed a bill to give the workers back pay when the government reopens.

The government doesn't seem to be opening anytime soon, since both President Donald Trump and Democrats are not budging from their positions regarding border-wall funding.

Friday was supposed to be payday for roughly 800,000 federal workers, but, because of the partial government shutdown, those employees have been seeing a big, fat $0 in their bank accounts.

Direct deposits for the pay period that ended on January 5 were sent out on Friday, but the entirety of the period was during the ongoing partial government shutdown — meaning that federal workers in the agencies that are closed received no pay.

A government shutdown occurs when the appropriated funding for federal agencies runs out and Congress has not passed new funding bills to allow the departments to spend more money, including on workers. A good (though admittedly simplistic) way to think about it is that the well has run dry as opposed to a dam holding up money that had already been set aside.

This shutdown does not affect all agencies, as Congress did pass funding bills for certain departments, including the departments of Defense and Energy, in September. But the shutdown has still resulted in closures for the departments of Agriculture, Commerce, Justice, Homeland Security, the Interior, State, Transportation, and Housing and Urban Development.

For employees affected by the shutdown, the lack of pay is a big deal. Employees going without pay owe more than $400 million in mortgage and rent payments, according to the real-estate portal Zillow. Federal workers have started GoFundMe fundraisers to try and cover medical costs and more during the shutdown.

Read more: Federal workers affected by the government shutdown have more than $400 million in mortgage and rent payments due this month, and it could cause chaos for the US housing market

According to the left-leaning Center for American Progress, each pay period missed means $2 billion is not going out to federal workers.

But there is some good news for these workers, though it may be of little comfort right now.

Excepted workers, the 420,000 employees who are being forced to work without pay, are automatically given back pay when the government reopens.

For furloughed employees, those who are barred from coming to work, Congress passed a bill on Friday that would provide back pay for the lost wages during the shutdown immediately after the government reopens.

But for federal contractors, employees of outside companies who are not direct government workers, may be left out in the cold. Some contractors will continue to employ and pay workers so that they are ready to get back to work as soon as the government reopens, but these third-party companies don't know when — or if — the government will reimburse them.

"With prior shutdowns, we've had instances where it's particularly hard for small businesses who have difficulty dealing with all this and fronting the money," Jessica Abrahams, a lawyer at Drinker Biddle who deals with government contracts, told NBC News.

As it stands, there seems to be no end in sight to the government shutdown — which will set the record for the longest funding lapse in history on Saturday — as President Donald Trump stands firm in his demands for $5 billion toward a wall on the US-Mexico border and Democrats stand firm on their refusal to give the president that money.