The Christmas carol begins; “While shepherds watched their flocks by night.” I was taught the only time shepherds watched their flocks was when the lambs have their young, which only happens in the spring of the year. Doesn’t that mean the Jewish month of Nissan (March-April) has to be when Jesus was born?
Someone has misled you. Shepherds watched their flocks through out the year to guard against wild animals attacking them and to keep them from just wandering off, as sheep are prone to do. The only time they didn’t do so is during the winter when cold weather required the flocks to be sheltered. This is one of the arguments against a December birth date for the Lord. The climate around Jerusalem can be quite cold and rainy during the late winter and would not permit pasturing flocks in the open fields. Most people prefer an early fall birth date.
There is a tradition that the shepherds were tending special Temple flocks the night the Lord was born. (Bethlehem is only 5 miles from Jerusalem.) These flocks were used as sacrificial animals and were bred to minimize the incidence of spots or blemishes that would have made them unsuitable for use. In a sense they were born to die for the sins of the people, which made them a strikingly clear model of the Lord Jesus, who was born for the same purpose. If this is true, it would have been fitting that the shepherds who watched over them were the first to learn of His birth.