Brexit supporters protest outside Downing Street in February 2019.Tolga Akmen / AFP / Getty

To understand how Britain has become so mired in crisis over its looming departure from the European Union, one first needs to understand the significance of its March 29 exit date.

Put simply: There is none.

March 29 marks two years since British Prime Minister Theresa May made the fateful decision to trigger Article 50, the EU’s time-limited exit procedure that formally began the process of Britain’s withdrawal from the bloc. The move followed immense pressure from Brexit proponents within the prime minister’s own party to enshrine an exit date into law.

Since then, March 29 has had an almost Independence Day quality to it. For many Brexiteers, it’s the looming reward after years of negotiations with Brussels on money, citizens’ rights, the Irish border, and everything in between. It’s the day, more than two and a half years since the Brexit referendum, when Britons can finally take back control.

But just because leaving the EU on March 29 is Britain’s legal default doesn’t mean it will necessarily come to pass. Most Brexit analysts will tell you it’s highly improbable—if not totally impossible—that the British government will ratify a withdrawal agreement (which has yet to be approved by Parliament) in the time remaining. This is especially true after the prime minister announced on Sunday that a parliamentary vote on her negotiated deal with the EU would be delayed further to March 12, a mere two and a half weeks before exit day.

That leaves the country with two equally unsavory options: to request an extension that would postpone its exit date from the EU by weeks, months, or even years, or to leave the bloc without a deal at all. May has said that she doesn’t believe the former should happen. A majority of parliamentarians say they won’t allow the latter (though it remains the legal default if no agreement wins legislative approval).

If March 29 symbolizes a day of independence for Brexiteers, it marks a source of foreboding for those who oppose leaving the EU without a deal. For them, it’s the deadline by which the British government has conceded that many of its existing trade deals will not be replicated. It’s the date that could mark the beginning of food shortages, delays at British ports, and other disruptions. It’s the day that could see the return of customs checks to the island of Ireland for the first time in decades.

Several British lawmakers are hoping to avoid these issues by postponing Britain’s departure until a deal can be secured—hopes that were bolstered on Tuesday when May announced that members of Parliament would get the chance to back a limited extension to Article 50 if they reject her deal and vote down leaving the EU without one. Such an extension would need to be made at the explicit request of the British government and would require the unanimous consent of the EU’s 27 other members. The bloc has already signaled that it would be willing to grant an extension, though only for a specific reason, such as to finalize an agreed deal or to hold a general election or second referendum.

Securing an extension won’t be easy. The idea of postponing Brexit beyond March 29 is seen as anathema to many Brexiteers who fear that a delay could lead to further government backsliding, and a number of Brexit-supporting MPs have threatened to rebel against the government, which has a flimsy majority, if it tries to pursue one. It’s also an unpopular idea for May, who has been reluctant to entertain any alternatives to her own negotiated deal. “I do not want to see Article 50 extended,” the prime minister told the House of Commons on Tuesday. “Our absolute focus should be on working to get a deal and leaving on the 29th of March.”

Even if the U.K. were to request an extension, the next question would be, For how long? This is something only the EU can answer. While a technical extension of up to a few weeks would be relatively straightforward for the bloc, a longer delay could pose issues—especially if it overlaps with the upcoming European Parliament elections. Speaking at an event in London last week, Stefaan De Rynck, the adviser to the EU’s chief Brexit negotiator, Michel Barnier, insisted that all EU members are required to participate in the May vote. “If you extend Article 50, you extend membership,” De Rynck said. “So you extend also all the rights and obligations of membership. There is an obligation of membership to organize European elections.”

Such is the latest conundrum of Brexit: Though the March 29 exit date itself doesn’t technically matter, any attempt to move it now does.

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