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

Isaac Newton, the renowned scientist and mathematician, lived during a time when dates and calendars were not standardized as they are today. This is why there are two different sayings of Isaac Newton's birth date:

1. December 25, 1642: Newton was born on this date according to the Julian calendar, which was in use in England until 1752. At the time, England had not yet adopted the Gregorian calendar, which is now the internationally accepted civil calendar.

2. January 4, 1643: If you were to convert Newton's birth date to the Gregorian calendar, it would be January 4, 1643. The Gregorian calendar, introduced by Pope Gregory XIII in 1582, was designed to correct inaccuracies in the Julian calendar by adjusting the method of calculating leap years.

The discrepancy arises because, although the Gregorian calendar realigned the date of the vernal equinox with the date used for calculating Easter, it took many countries, including England, a long time to adopt it. England did not switch from the Julian to the Gregorian calendar until 1752, which is well after Newton's death (he died on March 31, 1727, in the Julian calendar, or April 20, 1727, in the Gregorian calendar).

When discussing historical figures like Newton, it is important to consider the calendar system in use at the time to accurately understand dates and their modern equivalents.