English domestic and international rugby union is to be played over an expanded 11-month season under a new agreement that will run for four campaigns from 2019/20-2021/22, officials announced Tuesday.
Players will also have guaranteed in-season breaks, with a mandatory five-week post-season rest for all players, who will now be limited to 30 full-game equivalents, down from 32, in any one season.
The changes are part of a new structure that will see the Premiership final take place in late June, amid attempts by rugby union officials to produce a unified global calendar in San Francisco last year that balances the needs of the sport in both the northern and southern hemispheres, while addressing player welfare concerns in an ever-more physical sport.
Post-season tours by England, previously staged in June, will take place in July.
Twickenham will host the Premiership finals on June 20, 26 and 18 for the years 2020-22 with the campaigns starting on October 20, September 12 and September 18 respectively.
Traditionally, rugby union in England has been a winter sport, but a joint agreement between the Rugby Football Union, Premiership Rugby and the Rugby Players' Association will push the game into the summer months.
The new set-up will initially leave August as the only month without senior rugby union in England or abroad.
But in two years of the four-year cycle, when World Cups and British and Irish Lions tours take place, there will be Tests in August -- effectively leading to a 12-month season.
England internationals will play a maximum of 30 full games per season, reduced from 32, and be restricted to a limit of 35 match involvements of 20 minutes or more.
Despite concerns about maintaining public interest over a longer period, clashes with other sports and fears that players may be unable to mentally switch off, Premiership Rugby chief executive Mark McCafferty said the changes would benefit the domestic game.
"We've always held a view that the more rugby is played in better conditions and in better weather -- after the Six Nations - the better," McCafferty told a Twickenham news conference on Tuesday.
"It was then a question of how do we marry that up with the player welfare angle.
"It's always been the case that the Premiership's stronger attendances and stronger audiences are towards the business end of the season, but that's also because you've got the firmer grounds and better weather.
"Hopefully this new structure works on a number of fronts, but there's lots still to learn in the next three years. This is going to continue to evolve."
Meanwhile another feature of the new structure will see Lions tours, which take place every four years, reduced by one week to five weeks, with the combined side playing eight matches in total.
RPA chief executive Damian Hopley said: "It is fundamental that players had their say in the shaping of this new season structure".
He added the new agreement "gives players guaranteed in-season breaks for the first time and reduces playing thresholds".