The Third Age was a period that begun with the defeat of Sauron in SA 3434 to the rise and downfall of Sauron in TA 3002.
During a war between the Orcs and the Elves, Legolas' mother perishes in a battle in Mount Gundabad. (The Battle of the Five Armies)
At least five hundred years after the Last Alliance, the One Ring is picked up from the Anduin river by the Hobbit Deagol. However, his cousin Smeagol murders him and takes the Ring for himself. He later takes the ring into the Misty Mountains and hides in an underground cave. (The Return of the King, The Fellowship of the Ring)
Trivia
- Instead of 3019 years, the span of the third Age lasts for 3002 years. This is due to the seventeen year gap that is absent in the film.