Back in the 1980s, I went to a planetarium show that explored different astrological theories about the Star of Bethlehem. The narrator said that many scholars believed that Jesus was born in the springtime. I thought “more proof that the church is true.”
Over the years, I have read or heard various biblical experts say that Jesus was likely born in spring. I took my testimony boosts wherever I could find them.
When could Jesus possibly have been born and died? Christianity was a Mystery Cult like all the others, and their primary male deities died with the earth at the onset of winter--the Winter Solstice, which is around the 23rd of December--and were reborn in the spring. Note also that the Easter rebirth is calculated according to the lunar calendar as one would expect for a pattern that originated in the pre-Christian era.
The arguments about whether Jesus, who we don't even know existed as a individual person, was born on one day or another is getting lost in the weeds. Ockham would yield (hats off to S-Cat for that malapropism) his scythe ruthlessly in those pedantic fields.
A Catholic website uses the pregnancy of Elizabeth, the birth of John the Baptist, and the priestly rotation of the Baptist's father, Zechariah, to show the probability of Christ's birthdate on or around December 25:
"St. Luke related the announcement of the birth of St. John the Baptist to his elderly parents, St. Zechariah and St. Elizabeth. St. Zechariah was a priest of the class of Abijah (Lk 1:5), the eighth class of 24 priestly classes (Neh 12:17). Each class served one week in the temple, twice a year.
Josef Heinrich Friedlieb has established that the priestly class of Abijah would have been on duty during the second week of the Jewish month Tishri, the week of the Day of Atonement or in our calendar, between Sept. 22 and 30. While on duty, the Archangel Gabriel informed Zechariah that he and Elizabeth would have a son (Lk 1:5-24). Thereupon, they conceived John, who after presumably 40 weeks in the womb would have been born at the end of June. For this reason, we celebrate the Nativity of St. John the Baptist June 24.
St. Luke also recorded how the Archangel Gabriel told Mary that Elizabeth was six months pregnant with John (Lk 1:36)... Nine months from March 25, or six months from June 24, renders the birth of Christ at Dec. 25, our Christmas."
A common misconception is that Christians "stole" Saturnalia and adopted it as their own. There are several arguments against that, one being that Saturnalia was celebrated on December 17, and Christians had accepted 12/25 as "Christmas" long before Saturnalia became an official holiday. So it was not simply substituting a Christian purpose for a pagan one.
Another argument for Christ's birth in the Spring is that the shepherds had brought sheep to Jerusalem for Passover. True, that--but shepherds were ALWAYS brining sheep to Jerusalem for temple worship.
I had some cousins who got together every April 6 with the other side of their extended family regardless of what day of the week on which it fell. They drew names the year before, and each person gave the family member whose name he/she had drawn a hand-crafted or otherwise homemade gift. They called this holiday REAL Christmas.
Even my TBM parents found the whole thing to be gag-inducing. The aunt from that family who married into my family thought it would be a good tradition to start on our side of the family as well. She shared her idea with others in the family. My mom told her that it would make it tough for her if we all started celebrating REAL Christmas, too, because she wouldn't be able to attend the festivities for both families simultaneously. She then said, "I thought we could celebrate REAL Christmas for YOUR family on April 7 unless Easter happens to fall on that day. If that happens, we'll have to have your REAL Christmas on April 8." This particular aunt always insisted on spending actual holidays with her own extended family and only visited her husband's side (our side) a day or two after whatever holiday was being celebrated.
My dad then said, "There's nothing real about celebrating Christmas on April 7th or 8th. April 6 is bad enough. We'll just stick with the Catholics and the Protestants and the pagans and celebrate in December." All the way home he muttered to my mom about the ridiculousness of it all and about how the last thing in the world he needed was more hand-crafted garbage from relatives.