How long did the movie 'Avatar' take to make?

From original writing to release, it took about 15 years for Avatar to get to cinemas; the workings to create the movie itself took about 4 years.

James Cameron (writer/director/producer) had the idea and wrote an 80 page mini-script for the movie in 1994. Announcing in 1996 that he would begin making Avatar after the release of Titanic, Cameron was going to begin production in 1997 and planned to complete the film in 1999. Cameron soon decided that available technologies would not be able to properly create his vision, so he decided to put off making the film.

In 2005 Cameron began work on the movie again. The language development began, and in early 2006 he began work on the actual script, cultural development and components of his fictional universe. Principal photography began in mid 2007, with live photography starting in October of 2007. The official release date of the movie was December 18, 2009.
3 - 4 years ago or more. James Cameron thought of avatar after he finished off titanic