The APWU and the Postal Service have been meeting periodically at the headquarters level and have finally reached a tentative agreement on a method that will allow for locally-negotiated four-day workweeks.

“We have been pushing for a modified-workweek agreement seemingly forever: The first pilot programs were in 1994.”
 
The sticking point of the negotiations was the need to come up with a method that would allow for as many flexible work schedules as possible, which necessarily would have to be implemented on a facility-by-facility basis.

The agreement was set to be finalized the first week of October, with some local parties authorized to negotiate immediately..

We have been pushing for a modified-workweek agreement seemingly forever: The first pilot programs were in 1994. The 2000-2003 APWU-USPS Collective Bargaining Agreement — as well as a contract extension ratified Aug. 5, 2005 — also provided for the establishment of “modified workweek” pilot sites, with employees selecting work schedules of four 10-hour days.

Employees who want overtime may from time to time work a five-day schedule.
 
The pilot programs the last two years were frequently stymied and stalled by Area-level managers who restricted the pilots to a very limited number of post offices and areas within post offices.

This should be a giant step into the future for many postal employees. Changing a full day of work to a full day off for employees will dramatically change lifestyles. A side benefit of the elimination of a full day of work each week is that it reduces the amount of time workers spend getting to and from their jobs, which can only diminish congestion on the roads and help save energy. That’s a win for employees, the Postal Service, and our nation as a whole.

Employees who go on a modified workweek will work 10 hours a day straight time, and will receive penalty pay when they work more than 10 hours in a shift. Workers who like to work overtime should realize that while some straight-time hours and overtime hours will be available, if a sufficient number of employees choose a modified schedule — which is expected — overtime will be possible by working a fifth day.

Employees who want overtime may from time to time work a five-day schedule, but will forfeit their “third day off” in such weeks. Some employees who work the four-day schedule will not necessarily have the third day off consecutively with the other two.
source: American Postal Workers Union