are there two different sayings of isaac newton's birth date

Yes, there are two different dates often cited for Isaac Newton's birth: December 25, 1642, and January 4, 1643. This discrepancy arises due to the switch from the Julian calendar to the Gregorian calendar.

1. December 25, 1642 (Julian Calendar): Newton was born on Christmas Day according to the Julian calendar, which was in use in England at the time of his birth.

2. January 4, 1643 (Gregorian Calendar): When the British Empire adopted the Gregorian calendar in 1752, 11 days were dropped to align the calendar with the solar year. Additionally, the start of the year was moved from March 25 to January 1. As a result, Newton's birth date, under the Gregorian calendar, became January 4, 1643.

To provide some context:

• The Julian calendar was introduced by Julius Caesar in 45 BCE. However, it gradually fell out of synchronization with the solar year because it had a slight excess of days.
• The Gregorian calendar, introduced by Pope Gregory XIII in 1582, corrected this discrepancy by dropping 10 days and adjusting the leap year rule.

When converting dates from the Julian to the Gregorian calendar, one must account for both the accumulated difference in days and the change in the start of the year.

It's important to note that while Newton was born on December 25, 1642, in the Julian calendar, the more accurate representation of his birth date in our modern calendar system is January 4, 1643. However, it's common to see both dates mentioned, reflecting the historical context and the transition between calendar systems.