English domestic one-day cricket will revert to 50 overs from 2014, while LV= County Championship matches will usually begin on Sundays.
The England and Wales Cricket Board on Thursday announced the revised structure for the domestic game for the period from 2014 to 2017, having conducted a survey of more than 25,000 responses to the review of the game by former International Cricket Council president David Morgan.
A press release from the ECB confirmed the Championship will be retained as two divisions of nine teams apiece, with two teams promoted and relegated each season.
Each county will play 16 games, with the first 14 commencing on Sundays.
The FriendsLife t20 will be expanded from 10 to 14 group-stage games for each county, with most being played on Friday evenings after the ECB "noted the strong desire from Counties and spectators to create an 'appointment to view' for T20 cricket spread over a longer period of the season".
The top eight counties will progress to quarter-finals, with the winners going on to an unchanged Finals Day.
While the renamed Clydesdale Bank 50 has been expanded in terms of overs, the group stage will drop from 12 to eight games for each county. Eight teams will then advance to a straight knockout stage.
The ECB release noted: "There was no compelling preference from spectators for 40-over cricket rather than 50-over cricket, and therefore the format from 2014 will replicate the 50-over format played by the national team.
"Consistent with feedback from the players, there was a strong desire to retain the LV= County Championship in two divisions of nine teams."
ECB chief executive David Collier said: "The research study conducted by Populus was the largest piece of market research ever conducted on county cricket. The board agreed with the views of spectators and players in retaining a 16-match LV= County Championship which has proven very successful since its introduction in 2000."