With only six days left to act, the Senate is stalled on legislation that would make permanent the government's successful experiment with the four-day week and other flexible work hours programs.

The six-year old flexitime testing period is due to expire Tuesday unless it is made permanent by law.

About 20 percent of the Washington's area's 350,000 civil servants are now on some kind of flexitime. That includes the four-day week and set-your-own hours programs that allow workers to skip rush-hour traffic and expand service time to the public.

The flexitime experiment exempts Uncle Sam from the Walsh-Healy Act requiring payment for time worked in excess of eight hours a day. Unless the exemption is renewed, persons who are now on the 10-hour day (working four days a week) will have to go back to regular 8-hour day, 5-day week schedules. It is estimated that between 300,000 and 500,000 U.S. workers are now on some kind of flexible hours program.

The House long ago okayed making flexitime permanent. The White House also approves.

The hang-up is in the Senate. Sen. Orrin G. Hatch (R-Utah) wants to amend the flexitime bill to give government contractors the same overtime exemption, and to set a new (lower) minimum wage for teen-agers. Labor unions oppose both concepts.

Hatch believes contractors working with government agencies on the 4-day week should be able to adopt the same schedule without paying overtime penalties. He also argues that the lower minimum wage for teen-agers would open up jobs for that group, which has one of the highest unemployment rates.

But because of strong opposition to Hatch's two proposals, the federal flexitime bill hasn't been able to get on the Senate's calendar.

There is still time to save the flexitime program, but it is running out. Unless it is approved this week -- in time to get to the president for signature -- some people will have to make major schedule changes next week.