good catch...technically the only recognized presidents day excluding washington's birthday under 5 USCS § 6103 is Inauguration day.

(c) January 20 of each fourth year after 1965, Inauguration Day, is a legal public holiday for the purpose of statutes relating to pay and leave of employees as defined by section 2105 of this title [5 USCS § 2105] and individuals employed by the government of the District of Columbia employed in the District of Columbia, Montgomery and Prince Georges Counties in Maryland, Arlington and Fairfax Counties in Virginia, and the cities of Alexandria and Falls Church in Virginia. When January 20 of any fourth year after 1965 falls on Sunday, the next succeeding day selected for the public observance of the inauguration of the President is a legal public holiday for the purpose of this subsection.

The only legal hollidays are:
(a) The following are legal public holidays:
New Year's Day, January 1.
Birthday of Martin Luther King, Jr., the third Monday in January.
Washington's Birthday, the third Monday in February.
Memorial Day, the last Monday in May.
Independence Day, July 4.
Labor Day, the first Monday in September.
Columbus Day, the second Monday in October.
Veterans Day, November 11.
Thanksgiving Day, the fourth Thursday in November.
Christmas Day, December 25.

Then again I think you could argue that getting rid of Washington's day and replaceing it with Presidents day isn't taking away from Washington, MLK day could become Civil Rights day, Columbus day could become explorers day. Technically in so far as anyone celebrates these days, they are usually celebrated in a broader sense, and is it really fair that MLK get all the credit, or Washington, or Columbus? Harrison might have been a poor president but isn't he all but forgotten except by a few historians? Does it do a diservice to a person like Washington or MLK or Columbus that the day be viewed in a broader context than themselves? Also does it matter in terms of the statute on public hollidays that the only birthday is Washinton's and that Christmas isn't explicitly called Christ's birthday(of course most argue that it isn't historically)?

It is a correct statement to say that Washington's birthday is the only birthday that is a legal public holliday. If on such legal grounds(perhaps with historical questions about when he was really born) one argued that the birth of Christ was not the legally recognized reason for Christmas, and therefore could not be the reason for christmas one would be engaging in a form of intellectual silliness similar to argueing that Washington's birthday not be recognized as presidents day. Strict legalism when it comes to the meaning of words doesn't maintain but-for causation over the larger culture.

This is a neat example of culture trumping congressional statutues. Congress creates a holiday but doesn't ultimately control what or how that holiday is celebrated or marketed. Independence day can functionally be fireworks+watermellon day, Thanksgiving day can be Turkey day, Easter-chocolate bunny day. Mardi Gras flashing for beads and rum/kingcake day(can occur twice in a year in the unlikely case the Saints win a superbowl.)

Many of these "holidays" aren't even legal holidays because they don't fall under the statutory definition.

"(a) Holiday means the first day of January, the third Monday of February, the last Monday of May, the fourth day of July, the first Monday of September, the second Monday of October, the fourth Monday of October, the fourth Thursday of November, the twenty-fifth day of December, or any other calendar day designated as a holiday by Federal statute or Executive order."

Since my favorite president is Chester Arthur, and there just doesn't happen to be a federally-recognized "Chester Arthur Day," I long ago took to calling Washington's Birthday "President's (or is it Presidents'?) Day."

Whichever you prefer, since it's made-up anyway!