In July 2010, the organisers gave advance warning that the 2012 festival would be brought forward by two weeks at the request of the venue, in order to refurbish the Palais des Festivals.
The organisers say they have now been informed by the city of Cannes that the refurbishment has been postponed "for various internal and external reasons" and have decided to move the dates by popular demand.
Philip Thomas, Cannes Lions CEO, said: "We apologise to those who may have already made plans around the earlier dates, but after consulting with many people in the industry, there was an overwhelming view that our delegates would prefer to revert to the traditional Cannes Lions date. A time slot that has been in peoples' diaries for the best part of 60 years."
Instead of 3-9 June, the Cannes International Festival of Creativity will be held from 17-23 June.