Here are some key dates in the Greek debt crisis that has rumbled on for nearly six years.

-- 2009 --

- October: The Greek government of George Papandreou reveals that the national public deficit for 2009 was twice as much as thought -- at 12.7 percent of the country's output, instead of 6.0 percent. The figure is later raised again to 15 percent of gross domestic product (GDP).

- December: The three main credit ratings agencies -- Fitch, Standard & Poor's and Moody's -- downgrade Greece's debt.

-- 2010 --

- April: Ten-year bond yields leap above 8.5 percent, the highest since Greece adopted the euro in 2001. With public debt at 350 billion euros ($435 billion) and with bond yields surging -- making it unsustainable for Greece to borrow on the markets -- Athens appeals for aid from the EU and the IMF.

- May: Greece becomes the first eurozone country to receive a bailout as the EU and IMF announce a 110-billion-euro package in exchange for painful austerity measures, including harsh wage cuts and tax hikes.

-- 2011 --

- October: As Greece's economic situation deteriorates, the eurozone proposes a second bailout of 130 billion euros under which private sector creditors also agree to write off about half the debt owed to them.

-- 2012 --

- February: The eurozone approves Greece's second bailout package.

 - May 6: Greece's two main parties, the socialist Pasok and the conservative New Democracy, which both signed the austerity deals, suffer major losses in early elections. Radical leftwing group Syriza comes second. Attempts to form a government founder, forcing new elections.

 - June 17: The two main pro-bailout parties clinch enough votes to form a government in knife-edge elections, which fail to ease market fears about eurozone contagion. Conservative Antonis Samaras becomes prime minister and forms a three-party coalition.

-- 2014 --

April: Greece returns to sovereign debt markets for the first time in four years, and posts a primary surplus (which excludes debt interest payments) at the end of the year.

-- 2015 --

- January 25: Syriza, led by Alexis Tsipras, wins a snap election with a pledge to renegotiate the bailout terms. In five years, national output has been cut by 25 percent, salaries have fallen, and a quarter of the workforce is unemployed.

- February 20: Greece and its creditors agree to extend aid until the end of June. Athens pledges to come up with reforms in exchange for the last 7.2 billion euros in rescue funds.

- June 2: After months of bickering, creditors make a final pitch to Greece regarding the reforms deemed necessary.

- June 10: EU leaders reject a counter-proposal from Greece.

- June 30: Greece's bailout officially expires and the country defaults on a 1.5-billion-euro debt payment to the IMF.

- July 5: More than 61 percent of Greeks vote 'No' to creditors' bailout proposals.

- July 7: European leaders give Greece a final deadline of July 12 to reach a new bailout deal and avoid crashing out of the euro.

- July 9: Greece submits new bailout reform plans, less than two hours before a midnight deadline.

- July 13: July 13: After 17 hours of gruelling negotiations, Greece reaches a third bailout deal with the eurozone worth up to 86 billion euros ($96 billion) over three years but in return for more tough reforms.