What is celebrated and what is the origin of this American holiday?

(CNN) — This Monday is Presidents Day and George Washington's birthday. But is it really so?

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Americans haven't celebrated the nation's first president's birthday on his actual birth date in more than 50 years. Instead, in the United States, Presidents' Day is celebrated on the third Monday of February.

This is the explanation.

Washington's Two Birth Dates

Would you like to celebrate your birthday twice in a month? Washington did it during his presidency.

He was born on February 11, 1732, according to the Julian calendar then in use. But that changed when England and its colonies adopted the Gregorian calendar in 1752. His birthday was changed to February 22.

In the Gregorian calendar, a day is added to the calendar every four years to synchronize with the solar year. We know that extra day as a leap day.

Americans celebrated Washington's birthday on two dates during his presidency from 1789 to 1797. In 1885, February 22 was established as a holiday for Washington's birthday.

All this changed 100 years later.

Act on Monday holidays

In 1968, Congress debated whether the birthday celebrations of Washington and Abraham Lincoln, who were born on February 12, should be called Presidents' Day.

But legislators from Washington's home state of Virginia opposed it and the effort failed. However, Congress approved the Holiday Monday Act that year.

The law puts most of the nation's holidays on Mondays, leaving Americans with an occasional three-day weekend.

Eventually, the bill went into effect in 1971, and Washington's birthday celebration was moved from February 22 to the third Monday in February.

But still Not all states They celebrate President's Day.

Virginia still calls it Washington Day; Alabama calls it Washington Day, and Jefferson and Montana call it Lincoln and Washington's birthdays.