Transportation Secretary Ray LaHood. Charles Dharapak/AP Photo

Little is known about when, exactly, the "sequester" will wreak its expected havoc on the nation - but the process begins on Friday.

Each federal agency will implement its cuts differently, on its own timeline, and the White House Office of Management and Budget tells ABC News it does not have a calendar for what cuts will happen when.

The soonest-felt cuts will be to civilians working for federal contractors, who have been squeezed since late last year. Layoffs could happen right away, and President Obama will travel to a shipyard in Virginia today to highlight those cuts.

But we can guess that some of the worst purported consequences - of which agency heads have warned repeatedly - will come as a result of furloughs for government workers. Mandatory days off for TSA agents and air-traffic controllers will mean logjammed air travel, and fewer border patrol agents on duty will mean a more porous border, Transportation Secretary Ray LaHood and Homeland Security Secretary Janet Napolitano have said. Those furloughs will begin in April.

With that in mind, here's a basic timeline:

March 1 - Sequestration goes into effect. Barring a large deficit-reduction deal, or an agreement to cancel the sequester altogether, President Obama will be required to issue a sequestration order before midnight on March 1. His Office of Management and Budget (OMB) will submit a report to Congress. Federal agencies, which have already been drafting their sequestration plans according to OMB, will begin operating at reduced funding levels. The cuts will happen.

~March 4 - Furlough notices issued. If President Obama gives his order late at night on Friday, March 1, agencies could give notice to employees on the following Monday, March 4, that furloughs will be coming. Furloughed employees must be notified a month in advance, in most cases, according to Office of Personnel Management guidelines. Agencies can issue these notices before March 1, so it's possible federal employees will get word of furloughs this week. Agencies could also wait to issue furlough notices, hoping that a deficit deal comes quickly.

March 27 - The government runs out of money, or a new funding measure is passed. The federal government is currently being funded by a temporary measure that expires March 27. Congress and Obama will have to approve more funding in March, and while they've previously opted to continue the same funding levels, the March 27 deadline could provide a convenient time for them to strike a deficit deal, or at least modify the sequestration law to target the cuts differently.

~April 4 - Furloughs can begin, consequences are felt. This date is not definite, but it's a best guess. A wide array of agency-specific factors could mean different kinds of federal workers are furloughed at different times, according to an OMB official, but a 30-day notification timeline is the general rule - meaning government employees would start missing work a month after notices go out March 4.

It's not as if the entire federal government will shut its doors. Many furloughed employees will miss one day every two weeks - the Federal Aviation Administration, for instance, plans on cutting its workforce by that amount. But if the heads of federal agencies are to be believed - and hyperbole is possible - Americans can expect longer waits in the TSA line, fewer commercial flights, a more porous border, fewer workplace inspections, less meat and poultry production, and a host of miserable consequences arising from furloughed TSA workers, air traffic controlers, border-patrol agents, and OSHA and FDA inspectors.

Again, it's not certain that these purported consequences will begin happening April 4. Agencies have developed their own plans for implementing sequester cuts, and the timing could be different where different parts of the federal government are concerned. If any agencies have graded out their sequester plans, counting on Obama and Congress to reach a deficit bargain within a few weeks of the sequestration era, the worst of the cuts could be delayed.