Federal workers stand a good chance of getting a four-day Christmas holiday if President Reagan follows the custom of the White House.

Christmas Day this year falls on a Tuesday. The question many feds are asking is will they get a bonus day off on Monday, Dec. 24.

Getting the day off before or after Christmas is not unusual. For example:

* In 1969, President Nixon issued an executive order giving most federal workers the day off Friday, Dec. 26.

* In 1970, Nixon granted a half day of excused leave on Thursday, Dec. 24, for most federal workers.

* In 1973, Nixon again gave employes a double bonus, an extra long Christmas and New Year's weekend. Employes got Monday, Dec. 24 and Monday, Dec. 31 off.

* In 1975, President Ford gave most U.S. workers the day off on Friday, Dec. 26.

* In 1979, President Carter gave employes the day off on Monday, Dec. 24.

* In 1980, when Christmas fell on a Thursday, President Carter gave workers the day off on Friday, Dec. 26.

* Other special days off were granted Nov. 25, 1963, as a day of mourning for President Kennedy; on March 31, 1969, as a day of mourning for President Eisenhower; on Dec. 28, 1972, as a day of mourning for President Truman, and on Jan. 25, 1973, as a day of mourning for President Johnson.

Federal workers locally also have been given special days or time off by presidential directives. U.S. workers here -- but not in other parts of the country -- get Inauguration Day off. Next year they will get Monday, Jan. 21 off. In February 1983, Reagan granted federal workers two hours of administrative leave -- from noon to 2 p.m. -- to see the welcome-home parade for the Super Bowl champion Washington Redskins.

Top federal officials say that no decision has been made about the 1984 Christmas holiday policy. A White House aide said, "As far as I know the subject hasn't even come up." An official at the Office of Personnel Management said there is "no reason to believe" that the president will give employes the day off.

But the decision is yet to be made, and if the president follows tradition, workers could be in for a happy surprise announcement within the next few days.