More than 3000 workers at 70 companies will begin a four-day week with no loss of pay in a trial lasting six months.
From Monday, 70 companies have given their 3,300 employees a three day weekend without any reduction in pay. Instead, workers are asked to maintain 100% productivity for 80% of their time.
From a local fish and chip shop to large corporate companies, a wide range of businesses are taking part.
The programme, organised by academics at Oxford and Cambridge universities and Boston College in the US, will run from June to December, with a range of businesses and charities taking part.
Juliet Schor, professor of sociology at Boston College, and lead researcher on the pilot, said: "The four-day week is generally considered to be a triple dividend policy - helping employees, companies, and the climate. "Our research efforts will be digging into all of this."
There are 70 companies in the pilot but only 28 have publicly announced they are taking part.
