Every Christmas we celebrate the birth of Christ as December 25th. This date isn't very accurate according to most scholars, and the most sensible date that I've read dates His birth in late November of 5 B.C. King Herod died in 4 B.C., so it was sometime before then.
The date doesn't really matter, but sometimes I'm asked about it...so there's the extremely short answer.
For more on this, see Paul L. Maier, “The Date of the Nativity and the Chronology of Jesus’ Life,” in Chronos, karios, Christos: Nativity and Chronological Studies Presented to Jack Finegan [ed. J. Vardaman and E. M. Yamauchi; Winona Lake, IN: Eisenbrauns, 1989], 113–30).