What year is it? How long had Dantes been inprisoned?

In Chapter Fourteen, we learn that Dantes has been imprisoned for seventeen months.

“The 28th of February, 1815, at half-past two in the afternoon.”

“Today is the 30th of July, 1816,—why, it is but seventeen months.”

“Only seventeen months,” replied Dantès. “Oh, you do not know what is seventeen months in prison!—seventeen ages rather, especially to a man who, like me, had arrived at the summit of his ambition—to a man, who, like me, was on the point of marrying a woman he adored, who saw an honorable career opened before him, and who loses all in an instant—who sees his prospects destroyed, and is ignorant of the fate of his affianced wife, and whether his aged father be still living! Seventeen months’ captivity to a sailor accustomed to the boundless ocean, is a worse punishment than human crime ever merited.