The Trades Union Congress, the National Council for Voluntary Organisations (NCVO), Community Service Volunteers (CSV) and Volunteering England have made the suggestion.
An additional bank holiday between August and December would allow staff to volunteer for community projects.
Dame Elisabeth Hoodless, chief executive of CSV, said research shows the powerful effect volunteering can play in reducing stress and improving health.
"Volunteering re-energises workers at all levels and improves skills of communication, team-building and problem-solving," she added.
The Community Day, which could come into effect in 2010, would also allow parents to spend time with their children in the October half-term holiday.
People who are trying to balance their family and working lives need to be able to tell the difference between working hard and over-working, the Law Society says.
