How long is Odysseus held prisoner on Calypso's island?

Odysseus is held prisoner on Calypso's island, Ogygia, for seven years. During this time, Calypso offers him immortality and a life of comfort, but he longs to return home to Ithaca and his wife, Penelope. Ultimately, the gods intervene, and Hermes is sent to persuade Calypso to let Odysseus go.