When it comes to critical elements of the sequester timeline, not much is known -- because federal agencies have been tight lipped.
Asked when specific effects will be felt, officials at three federal departments declined to discuss the timing of sequester cuts and their consequences. Some departments were waiting for President Obama's Friday night sequester order and subsequent guidance they expected to receive from the Office of Management and Budget before talking about what would and wouldn't happen and when.
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"There's no calendar of dates for specific actions or cuts on specific dates," Department of Health and Human Services public affairs officer Bill Hall told ABC News. "Again, these cuts need to be applied equally across all agency programs, activities and projects. There will be wide variation on when impacts will occur depending on a given program."
Some cuts won't be felt for a while because they have to do with government layoffs, which require 30 days notice, in most cases.
For instance, the Federal Aviation Administration won't begin layoffs until at least April 7, one FAA official estimated.
But some cuts don't involve furloughs, and could conceivably be felt immediately.
The Department of Homeland Security declined to comment on the timeline of layoffs to cybersecurity contractors and first responders funded through states, as well as limited Coast Guard operations and cuts to FEMA disaster relief.
The Department of Housing and Urban Development said it could not comment on cuts to housing vouchers, rent assistance for AIDS patients, maintenance for housing projects.
The Department of Health and Human Services declined to discuss the specific timing of cuts to Head Start services, low-income mental-health services, AIDS/HIV testing, and inpatient substance-abuse treatment.
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So even as the sequester hits, we still don't know when some of its worst effects will be felt.
Here's what we do know:
What Will Happen Saturday
Air Force Training. At a briefing Friday, Deputy Defense Secretary Ashton Carter warned that "effective immediately, Air Force flying hours will be cut back."
More from Carter, via ABC News' Luis Martinez: "What does that mean for national security? What it means is that as the year goes on, apart from Afghanistan, apart from nuclear deterrence through two missions we are strictly protecting, the readiness of the other units to respond to other contingencies will gradually decline. That's not safe. And that we're trying to minimize that in every way we possibly can."
Closed Doors at the Capitol. ABC News' Sunlen Miller reports that Capitol Police issued a memo announcing it would have to close some entrances to the Capitol, writing: "At this time it is anticipated that the U.S. Capitol Police will be required to close some entrance doors and exterior checkpoints, and either suspend or modify the hours of operation for some of the U.S. Capitol Complex posts located inside and outside of the CVC and Office Buildings."
Capitol Janitor Furloughs. After President Obama warned that janitors at the Capitol will be furloughed, ABC News' Sunlen Miller reported that was not entirely true: The Senate sergeant at arms, Terrance Gainer, told ABC News that no full-time salaried Capitol Police officers would face furloughs or layoffs at this time. They will, however, see a "substantial reduction in overtime," Gainer told ABC News.
Delayed Deployment for USS Truman Aircraft Carrier. This has already happened, the Associated Press reported Friday morning: "One of the Navy's premiere warships, the aircraft carrier USS Harry S. Truman, sits pier-side in Norfolk, Va., its tour of duty delayed. The carrier and its 5,000-person crew were to leave for the Persian Gulf on Feb. 8, along with the guided-missile cruiser USS Gettysburg."
What Won't Happen Saturday
Many of the sequester's worst consequences purportedly will arise from government worker furloughs, which can't happen right away. In most cases, government workers must be notified 30 days before their workdays are cut and, in some cases, longer, according to Office of Personnel Management Guidelines.
Here are some sequester effects that won't befall us until early April at the soonest:
Fewer Commercial Flights. Transportation Secretary Ray LaHood has warned that fewer air traffic controllers could mean backed up commercial air traffic. An FAA official estimated that furloughs won't begin until April 7.
Fewer FBI Agents and a Greater Threat of Terrorism. FBI Director Robert Mueller has warned that cuts at the FBI will weaken the bureau's capability to break up terrorist plots. Those warnings have centered on FBI furloughs, which can't begin immediately. The FBI would not comment on the timing, and the Justice Department did not respond to ABC News' request for comment.
Longer Airport Security Lines. TSA workers won't be furloughed immediately. Instead, the agency intends to first implement a hiring freeze. That, along with cuts to overtime, will mean airport security lines gradually will get longer, but they won't be backed up this morning.
A statement from TSA, provided to ABC News: "Travelers will likely not see immediate impacts at airport security checkpoints on March 1, but lines and wait times will increase as reductions to overtime and the inability to backfill positions for attrition occur. While wait times can vary on a number of factors, if sequestration goes into effect, TSA will put in place a hiring freeze, which will result in up to an additional 1,000 TSO vacancies by Memorial Day weekend and up to 2,600 vacancies by the end of the fiscal year. With TSA staffing levels decreasing over time, we expect that during busy travel periods wait times exceeding 30-40 minutes could double at nearly all of the largest airports. In addition, passengers who schedule their travel outside of peak flight schedules and plan to arrive close to their scheduled flight time may see their wait times now reach 30 minutes or more."
More Porous Border. Homeland Security Secretary Janet Napolitano has warned that furloughs to Customs and Border Patrol personnel will make it difficult to maintain security across U.S. borders. Again, this possibility rests on furloughs that can't happen immediately.
Smaller Medicare Payments to Doctors, Hospitals. While Medicare benefits are protected, payments to Medicare providers (doctors and hospitals) will shrink by 2 percent. That won't happen until April 1, according to the Center for Medicare and Medicaid Services (CMS). The CMS says cuts will also affect Parts C and D: "Furthermore, CMS is prepared to take sequestration into account when they calculate the April monthly payment amount for Part C and D plans on March 21st and communicate the amount to plans on March 22," an official said.
What Won't Happen at All
Sequestration was advertised as "across-the-board cuts" but, in reality, it doesn't touch everything. Certain mandatory entitlement programs are completely exempt from sequestration cuts.
Here are some of them, as outlined in a Jan. 10 Congressional Research Service (CRS) report on the sequester:
Social Security Benefits. The Social Security Administration warned that once staff furloughs begin, the administrative cuts will mean slower processing for disability claims. But Social Security checks themselves will not shrink.
Medicare Benefits. Payments to providers will shrink 2 percent beginning April 1, meaning "$11 billion in lost revenues to Medicare doctors, hospitals, and other providers," according to CMS -- but actual Medicare benefits are protected from the sequester.
VA Programs. "All programs administered by the VA, and special benefits for certain World War II veterans," will be exempt from sequestration cuts, according to CRS.
Pell Grants. Completely exempt from sequestration cuts, according to CRS.
Medicaid. Completely exempt from sequestration cuts, according to CRS.
Welfare, technically called Temporary Assistance for Needy Families (TANF). Completely exempt from sequestration cuts, according to CRS.
Food Stamps, technically called Supplemental Nutrition Assistance Program (SNAP). Completely exempt from sequestration cuts, according to CRS.
Children's Health Insurance Program (CHIP). Completely exempt from sequestration cuts, according to CRS.
"Child Nutrition Programs (including school lunch, school breakfast, child and adult care food, and others, but excluding special milk)" will all be completely exempt, according to CRS.
The Special Inspector General for TARP won't lose funds, along with a few other administrative programs related to economic recovery, according to CRS.
Delayed Tax Returns. ABC News' Devin Dwyer reported that the IRS told ABC News the sequester will not delay tax refunds and may mean fewer audits. The agency has warned its employees to expect furloughs, but not until this summer -- after tax season ends.