The calendar says there are 13 months left to Barack Obama’s presidency. But when it comes to exercising executive power, it’s more like five.

Nearly 4,000 regulations are squirming their way through the federal bureaucracy in the last year of Barack Obama’s presidency — many costing industry more than $100 million — in a mad dash by the White House to push through government actions affecting everything from furnaces to gun sales to Guantánamo.

That means a full court press at the Occupational Safety and Health Administration (OSHA) to reduce exposure limits for silica, a chemical used widely in construction and fracking that can cause cancer when inhaled; at the Bureau of Alcohol, Tobacco, Firearms and Explosives, to require more small-scale gun sellers to perform background checks; and at the Food and Drug Administration, to make food manufacturers disclose on product labels how much sugar they add to cranberry juice.

Much of this work will be carried out in the coming months by career bureaucrats working in the bowels of federal agencies, but the cumulative effect adds up to something larger: A final-year sprint by a president intent on using executive power to improve the lives of American workers and consumers — in many instances over loud objections from the businesses that will have to pay for it.

The work must be done swiftly in most cases because any regulation finalized after May 17 or thereabouts risks being blocked by Congress.

That leaves plenty of time for the rule on silica, but not for one on beryllium, even though both chemicals pose grave health risks.

There’s likely sufficient time to regulate small-scale gun sellers, but not if the threshold is some specific number of guns sold.

The list could go on for thousands of regulations, and while Obama’s executive agencies are intent on pushing through the president’s priorities without congressional interference, industry lawsuits and congressional hearings will surely slow the Obama regulation freight train.

“The regulatory state has grown under this administration seemingly without regard to the costs, practicality, or even legality, of rules pushed through by federal agencies,” Chamber of Commerce President Thomas J. Donohue complained in an email. “The president’s hurry-up approach of executive orders and rushed rulemakings is no way to govern a representative democracy.”

But Obama, facing a Congress that will likely be in a less bipartisan mood than in 2015, is

undeterred. “I plan on doing everything I can,” he said Dec. 18, “with every minute of every day that I have left as president to deliver on behalf of the American people.”

The mid-May deadline isn’t statutory or in any way official, but neither is it arbitrary. It arises from the Congressional Review Act, a 1996 law that gives Congress 60 legislative days to veto, by a special swift procedure, any regulation it dislikes before the rule takes effect.

The president may veto Congress’s veto, as Obama did the one time he faced this situation. But if the 60-day period extends past the inauguration of a new president, and if that president is of the opposing party — a President Donald Trump, say, or Ted Cruz or Marco Rubio — any resolution of disapproval against his predecessor will surely go unchallenged.

That worry isn’t theoretical. Early in 2001, incoming President George W. Bush let stand a resolution of disapproval against an ergonomics rule that OSHA was foolish enough to issue two months before Bill Clinton vacated the West Wing. The regulation vanished into thin air.

But don’t 60 days after mid-May take you to mid-July rather than late January 2016? No, because these are legislative days, which typically come only three per week, in weeks numbering far fewer than 52. The partisan gridlock of recent years has shortened the legislative calendar even further.

It was Sam Batkins, director of regulatory policy at the conservative American Action Forum, who examined preliminary House and Senate calendars for 2016, drawing on what he modestly calls his “shoddy math skills,” and decreed that any regulation issued on May 18 or later would be vulnerable to a congressional resolution of disapproval fielded by Obama’s successor.

That deadline is a soft one, because Congress might push the May deadline back by adding, for instance, a lame-duck session after the 2016 election. But Ronald White, who is director of regulatory policy at the liberal Center for Effective Government — and doesn’t agree with Batkins about much — endorses his mid-May deadline as the most plausible and prudent one to eliminate any possibility of congressional reversal.

Here’s a rundown of Obama’s better bets:

Gun control: In the aftermath of mass shootings in San Bernardino, Calif., Colorado Springs, Colo., and Charleston, S.C., the Obama administration has been “scrubbing” the books for possible executive actions, given Congress’s reluctance to enact any form of gun

control. This week it’s expected to tweak an existing BATFE rule to require more gun sellers to get a license — and therefore do background checks on customers no matter where they sell. The “engaged in the business rule” requires sellers to get a license if gun sales is their “livelihood,” but the rule is comically vague about what “livelihood” might mean in this context (“the repetitive purchase and resale of firearms”).

Obama may clarify the definition to include any guns sold in their original packaging or re-sold shortly after they’re acquired. Alternatively, he may have it turn on how many guns are put up for sale, or on whether more than 25 guns are sold in a given year. A numerical limit, though, might require drafting a regulation, which would likely stretch beyond the soft May deadline. (A regulation traveling through the bureaucracy at breakneck pace can be finalized in perhaps a year.) The likeliest possibility is that Obama will offer a so-called “factor test” that will lay out a variety of criteria to indicate whether a seller is likely to need a license.

In addition, BATFE may soon finalize an August 2014 rule requiring all licensed dealers and manufacturers to report as missing to federal authorities any guns that are stolen in transit to a buyer. (Stealing unregistered guns is easier than stealing registered ones because they’re harder to trace.)

Nutritional labeling: In March 2014, Michelle Obama held a ceremony in the East Wing to introduce a design overhaul of food nutrition labels. These were so confusing, she said, that “unless you had a thesaurus, a calculator, a microscope or a degree in nutrition, you were out of luck.” The most controversial proposed change was a new requirement that the labels disclose how much sugar food makers added to their products.

Much of the food industry opposes the plan, arguing that it will confuse consumers. The American Sugar Association has all but threatened to sue over the change. But two food behemoths – Nestlé and Mars — support the change, saying more transparency is good, and that added sugar is a problem in the American diet.

The rule would also update serving sizes for some products to bring them closer to the amounts people actually consume. The serving size for ice cream, as an example, would go from half a cup to a full cup, doubling the number of calories per serving. And speaking of calories, the FDA has proposed enlarging their font size on food labels.

The final nutrition reg is expected in March, at an estimated one-time cost to the industry, the FDA says, of $2.3 billion (and a benefit estimated at $21.1 billion to $31.4 billion over 20 years).

E-cigarettes: The FDA also has in the works a rule extending its jurisdiction to e-cigarettes, which have become wildly popular with teenagers. (Last spring the Centers for Disease Control and Prevention reported that e-cigarette use by high school students tripled in 2014 to 13.4 percent.) The rule, which may ban the use of e-cigarettes by anyone under the age of 18, was first proposed 20 months ago, and a final version has been awaiting clearance from the Office of Management and Budget since October. “They’re being marketed to youth,” says the Center for Effective Government’s White. “It’s a huge problem.” Depending on the final composition of the rule, which may regulate other new tobacco products as well, its cost over 20 years could be anywhere from $20 million to $810 million, which might well put e-cigarettes out of business.

Retirement advice: By the end of March, the Labor Department is expected to publish a regulation requiring brokers who offer advice about retirement investments to do something that many assume (incorrectly) they have to do already: namely, consider only the best interests of the investor. In fact, the brokers often take into account fees and commissions to steer customers into one investment or another. The White House Council of Economic Advisers calculates that such conflicts of interest fleece consumers of about $17 billion annually. The Labor Department calculates that complying with the rule will cost industry $2.4 billion to $5.7 billion over 10 years.

The financial industry, congressional Republicans, and even some Democrats oppose the “fiduciary rule” on the grounds that it will make it more difficult for investors to acquire investment advice at a cost they can afford. “I will continue this fight until the rule is delayed, dismantled and defeated,” Rep. Ann Wagner (R-Mo.) said in December. Wagner authored a bill to halt the rule that cleared the House in October.

Supporters expect the final rule to be softened for businesses. Changes that expand exemptions for small businesses, simplify disclosure, and broaden the definition of what’s financial “education” and not “advice” are top fixes that the Chamber of Commerce seeks that won’t likely trouble the rule’s advocates. “Firms’ ability to market their services without triggering investment advice, they’ll fix that,” said Barbara Roper, an official with the Consumer Federation of America, a liberal-leaning advocacy group. “That does not undermine protections for investors,” she said.

But the threat of a lawsuit to hangs over even a modified rule. “Our sense is that the effort to combat the DOL’s fiduciary standard rule will move to the courts following its final release” in the first quarter of 2016, Isaac Boltansky, an analyst with Compass Point LLC, said in a Dec. 16 research note.

Energy efficiency: The Energy Department is working on dozens of new or updated efficiency standards for computers, gas furnaces, dishwashers, pool heaters, air conditioners, walk-in coolers and freezers, vending machines, ceiling fans, fluorescent lamp ballast, boilers, ovens, and hearths. The efficiency measures don’t typically generate much attention because they’re, well, just a little bit boring, even to POLITICO Pro’s intrepid policy jocks. But they’re expected to save consumers a lot of money, and also — along with already-completed rules on ice makers, industrial lamps, electric motors, and other products — to generate roughly half the carbon emissions cuts that the Obama administration pledged to deliver before the Paris climate talks.

The energy standards can also be rather expensive, a fact that’s caught the eye of the American Action Forum. The furnace rule’s cost will vary according to region and furnace type, but AAC’s Sam Batkins puts it at $741 million annually, making this — to industry, anyway — the most costly regulation in the pre-May 18 batch.

Teacher prep: The Education Department is set to publish as early as this month a long-delayed and contentious final rule overhauling how teachers are prepared for the classroom. The rule would cut off federal funding for any teacher prep programs that prepared their graduates poorly.

The Education Department said last year that implementing the rule would cost states and providers $42 million over 10 years (possibly less due to “due to technology and other efficiencies”). But advocacy groups, states, and teacher prep programs complain that it will cost far more; for example, the California Commission on Teacher Credentialing said it could cost the state $485 million just in the first year.

Workplace hazards: OSHA has been working quite literally for decades on a regulation that would lower drastically the permissible exposure limit to crystalline silica. The construction industry has fought the rule tooth and nail, citing its high cost; health advocates have fought just as hard in favor, citing the severe health consequences of a high exposure limit, which include lung cancer. In September 2013, OSHA proposed a rule that would reduce the permissible exposure limit to 50 micrograms per cubic meter. OSHA estimates the rule will save more than 600 lives and prevent more than 1,500 new cases of silicosis each year. The construction industry, the foundry industry and other businesses oppose the rule, saying OSHA has vastly underestimated (at $637-$658 million) its implementation costs.

Gitmo: On his first day in office Obama ordered that the terrorist prison at the U.S. naval base in Guantánamo Bay, Cuba, be shuttered. The prison, established by President George

W. Bush early in 2002 to hold Al Qaeda and Taliban prisoners for trial by military tribunal, had drawn condemnation from the international community and human rights groups. But the closure didn’t happen, because Congress moved immediately to bar any Gitmo inmates from being transferred to the U.S., or any new prison facilities built to house them. Eventually it was worked out that the Obama administration would furnish Congress with a plan for closing the prison. But the White House earlier last month rejected as too expensive a draft road map to transfer Guantánamo’s remaining inmates to one of several federal prisons or military facilities in Kansas, Colorado, or South Carolina, and sent it back to the Pentagon for revisions.

Many of the remaining 107 detainees are slated to be sent to other countries, and some face military prosecutions. But at least several dozen are likely to remain in custody because the U.S. government deems them too dangerous to release, or lacks sufficient evidence (or will) to prosecute them.

The big question for this year is whether Obama will try to go around Congress in a last-ditch attempt to close the prison by invoking his executive authority as commander- in-chief. Last month Cliff Sloan, who served as special envoy for Guantánamo closure from 2013 to 2014, and Gregory Craig, Obama’s White House counsel in the first term, wrote in an op-ed that “Under Article II of the Constitution, the president has exclusive authority to determine the facilities in which military detainees are held. Obama has the authority to move forward. He should use it.”

At a December 18 press conference, Obama indicated that he’ll send proposed legislation to Capitol Hill first, then ponder his unilateral options should that gambit fail. If he proceeds, Obama’s most valuable Gitmo ally—his 2008 adversary John McCain, who shares Obama’s desire to close the prison–may then become his chief obstacle. That’s because McCain has threatened to sue if Obama bypasses Congress. Should that occur, we’ll see a rematch of Obama v. McCain — though possibly with neither man in residence at 1600 Pennsylvania Ave.

Brian Bender, Paul Demko, Caitlin Emma, Alex Guillén, Jason Huffman, Marianne LeVine, Brett Norman, Patrick Temple-West and Sarah Wheaton contributed to this report.

Correction: An earlier version of this piece referred to Sam Batkins, erroneously, as “Dan.”