The Nativity : Chapter 12-106

1582 A.D., St. Gregory XIII adopted the new calendar
The Julian calendar had 365.25 days.
On the other hand, the Gregorian calendar had 365.2425 days and several conditions.
St. Gregory XIII deleted ten days from the calendar, thus the next date of October 4 became October 15 of 1582 A.D.
Shortly speaking, the old solar calendar of the ancestor of St. Abraham which began in about 2558 B.C. was twenty days longer in A.D. 2, than the old Gregorian calendar of the Astronomy, so the winter solstice changed from January 1 to December 12.
The Gregorian calendar is perfect calendar.
That is, if the Jews began their solar calendar, their solar calendar was one day longer than the Gregorian calendar of the Astronomy per 128 years.