"Presidents' Day"

5 U.S. Code § 6103 - Holidays

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.

So if this "Presidents' Day" isn't a legal holiday, it must be an illegal one, right?

(It's not on the Connecticut list of "Days designated as legal holidays," either.)