How many years did it take to accomplish 12 Labours of Hercules?

The Twelve Labours of Heracles or Hercules are a series of episodes concerning a penance carried out by Heracles, the greatest of the Greek heroes, whose name was later romanised as Hercules. They were accomplished over 12 years at the service of King Eurystheus.

Driven mad by Hera, Heracles slew his own children. To expiate the crime, Heracles was required to carry out ten labours set by his archenemy, Eurystheus, who had become king in Heracles' place. If he succeeded, he would be purified of his sin and, as myth says, he would become a god, and be granted immortality.

Despite the difficulty, Heracles accomplished these tasks, but Eurystheus in the end did not accept the success the hero had with two of the labours: the cleansing of the Augean stables, because Heracles was going to accept pay for the labour; and the killing of the Lernaean Hydra, as Heracles' nephew, Iolaus, had helped him burn the stumps of the multiplying heads.

Eurystheus set two more tasks, fetching the Golden Apples of Hesperides and capturing Cerberus. In the end, with ease, the hero successfully performed each added task, bringing the total number of labours up to the magic number twelve.