Happy Birthday Mr. President.

It’s important to note that the presidents Washington, Lincoln, and Reagan were born according to the Julian calendar used in the American colonies. However, Washington’s birthday was moved to February 11 when the Gregorian calendar was adopted in the late 18th century, whereas Lincoln’s birthdate remained the same.

Julian Calendar and the Gregorian Calendar

1. The Julian and Gregorian calendars are solar calendars used to determine the date and time of various events, including religious holidays, political events, and astronomical observations. However, there are several key differences between the two calendars:
2. Origin: The Julian calendar was introduced by Julius Caesar in 45 BC and was named after him. The Gregorian calendar was introduced by Pope Gregory XIII in 1582 and is named after him. Leap Year Rule: The Julian calendar added an extra day to the calendar every four years to account for the extra day in a leap year. However, this rule could have been improved and led to accumulated errors. The Gregorian calendar refined this rule so that only years divisible by 4 are considered leap years, except for years divisible by 100 but not divisible by 400.
3. Number of Days in a Year: The Julian calendar year is 365.25 days long, while the Gregorian calendar year is 365.2422 days long.