Republicans have huge ambitions for this Congress. They’re already running short on time.

On Friday, the Senate confirmed Supreme Court nominee Neil Gorsuch before heading out of town for an 11-day recess.

When they return to the Capitol on April 22, they’ll almost immediately run into a hard deadline: Congress has until April 28 to pass a new budget to avert a government shutdown, or pass a “continuing resolution” to temporarily lock last year’s funding for the government in place. If they fail to do either, Donald Trump’s 100th day in office — April 29 — would be marked by a government shutdown.

Passing a new budget would require Congress to come to some sort of an agreement about Donald Trump’s request for additional military spending and money for his proposed Mexican border wall — no sure bet. Passing the temporary “continuing resolution,” which includes funding for Obamacare, would probably be easier, but it would also force Republicans to eat up even more time on their legislative calendar debating budget levels, rather than advancing the legislation they promised during the campaign.

“It’s going to be tight. They’ve got to accelerate it: The first 100 days are almost already gone,” said Sen. Ron Wyden (D-OR). Asked if Republicans should be worried that they don’t have nearly enough time to clear their legislative plate, Wyden responded: “You’re making a lot of sense.”

Below is the schedule of internal House Republican deadlines, as leaked to Politico. So far, only the Fiscal Year 2017 Budget has been checked off:

In an interview, a spokesperson for Senate Majority Leader Mitch McConnell (R-KY) said that Democrats and Republicans on the appropriations committee were getting close to a deal for a new budget and had confidence it could be wrapped up by April 28. “Negotiations have been going on for weeks,” said Don Stewart, McConnell’s deputy chief of staff, in an interview last week. “The deadline is still three weeks away, and they’re getting close.”

But some experts were not so confident the rest of the Senate would go along with what the appropriations committee wants, suggesting another delay in passing the budget. “Congress would have to act quickly, it would have to be forced through and rank-and-file members wouldn’t have much of a chance to review or change it,” said Ed Lorenzen, senior adviser for the Committee for a Responsible Federal Budget. “So they may prefer to kick the can down the road with a CR instead.”

But if Republicans clear the hurdle of a potential government showdown by prolonging budget negotiations, the Senate’s breakneck schedule won’t allow that much time to come to a resolution. Senate Republicans say they want to accomplish big legislative projects — tax reform, a health care overhaul, debate over intervention in Syria, perhaps an infrastructure project — while also leading investigations into things like Donald Trump aides’ potential ties to Russia.

Then things could really get intense around late August or early September, when the Treasury Department is projected to hit the “debt ceiling” — without raising it, the US would default on its debts and cause a cataclysmic shock in the global economy. In addition, they’ll have until October 1 to set the budget levels for Fiscal Year 2018. (Though they can again pass another continuing resolution, should it come to that.)

Right now, Senate Republicans say they still think they have time to accomplish their big-ticket items, though they also blame Senate Democrats from preventing them from doing more.

“Is it too fast? No,” said Sen. Richard Burr (R-NC). “And the minority eats up all the time, filibustering a justice nomination — and that limits the number of legislative days we have.”

But Sarah Binder, a congressional expert at the Brookings Institution and George Washington University, argued that the key problem is that Republicans have not been able among themselves to determine what legislation they want to pass.

“The calendar is up to Republicans: They have to decide what they’re going to do legislatively, and how they’re going to do it,” Binder says. “They have to make a decision: are they serious about reviving health care reform, do they want to do tax reform first, do they want to try to do both of them?”

For instance, Republicans have said they want to use a fiscal year 2018 reconciliation bill to pass tax reform. But under the Congressional Budget Act, Binder says, once Republicans adopt the FY18 budget resolution that sets up the FY18 reconciliation bill, the FY17 reconciliation bill that Republicans planned to use for health care reform would likely no longer be operative.

Republicans, she says, still have time to figure out how they want to proceed. But they’re running out of it.