Most Americans consider Feb 22nd to be George Washington's birthday, as that is what we are taught in school. And we assume everything we are taught in school is correct.
However, the "Father of our Country" was born prior to that pesky Julian/Gregorian calendar switch. According to the Julian calendar, he was born on Feb 11, 1731. According to the Gregorian calendar, he was born on Feb 22, 1732. You decide how old he is.
When the Federal Government moved George Washington's birthday to "The Third Monday in February" they made it impossible for it to ever be celebrated accurately on either calendar, as the earliest it can fall is Feb 15, and the latest it can fall is Feb 21.
The National Archives explains that there is no such Federal Holiday as "President's Day" and the 3rd Monday in February is only for George. It isn't for Abe or any other presidents.
Curiously, Abe's birthday was Feb 12th, so arguably, if there were a Federal Holiday honoring both Presidents, it might be better situated on the Second Monday, as that should fall in the same week as the 11th and 12th each year.