Flexitime is alive! So are the four-day week, flexitour, modified flexitour, variable day, gliding schedule and modified gliding schedule, variable week, maxiflex and other forms of alternate work schedules that permit 575,000 government employes to work something other than the standard eight-hour day or five-day week.

Temporary legislation to extend the flexitime program cleared the House Tuesday and has gone to the president. He will sign it. That will permit thousands of workers here -- from Reston to Fort Meade -- to keep their schedule of 10-hour days, four-days a week, or other programs in which they waive overtime to alter their workday schedules.

The 120-day extension will keep the various flexitime programs -- some of them would have died Monday -- alive pending approval of permanent legislation. Sen. Ted Stevens (R-Alaska) hopes to get a bill through committee Monday that meets the approval of the Reagan administration and most federal employe unions.

Stevens' bill would give agency managers authority to terminate a flexitime program when they feel it is hurting productivity or adding to operating costs. The American Federation of Government Employees wants legislation that will protect programs provided by union contract from arbitrary cutoff by management.

Here's a partial glossary of major alternate work schedules:

Flexitime: That is the catchall name for various programs where fixed arrival and departure times are replaced by a work day that allows employes to come and go largely as they please, provided they are on the job for specified hours each day, and they put in eight full hours every day.

Credit Hours: For the past three years, agencies have been allowed to experiment with a variety of tours that permit employes to work more than eight hours daily (without overtime) and get credit for the extra time so they can work four-day or even three-day weeks, so long as they put in 80 hours of work every two weeks.

5-4/9 Plan: This program, covering about 100,000 workers, allows employes to get a three-day weekend every other week. They can do it by working almost nine hours a day for five days, then almost nine hours a day for four days and take the 10th day off.

If the flexitime program dies out after the extension, all employes working four-day weeks, three-day weeks, the 5-4/9 tours or other schedules where they get time credit for work in excess of eight hours a day will have to return to the regular eight-hour day, five-day week.

In addition, people on flexitime could be put back on fixed schedules if their agencies decided to do it. But for now the flexitime program, in all its forms, is alive for at least 120 days.