"If Luke's account has any historical basis, therefore, Jesus is likely to have [sic] born in the summer." (Porter, 2004, p. 70)
"...the chances that Jesus was born on December 25 are 1 in 365 (or 366 in leap years). This date was invented by the Western church - as late as the fourth century under the emperor Constantine - as a way to replace the pagan festival of the Unvanquished Sun, and is first attested, to be precise, in a Roman calendar in AD 334." (Vermes, 2006, p. 3)
"According to age-old local custom, shepherds kept their flocks out in the fields between March and November. This would place the Nativity not in the winter season of Christmas, but sometime between spring and autumn." (Vermes, 2006, p. 91)