The following quotes are taken from the underlined saints. The exact reference may be found in the bracketed source below each quote. The notes after each quote are brief explanations of information which may need to be clarified relating to the relevant quote.
The Constitutions of the Holy Apostles
"Brethren, observe... the birthday which you are to celebrate on the twenty-fifth of the ninth month..." (Book V, ch. XIII, section III)
April was the first month and, as is well known, this led to April Fools' Day being established. The ninth month from April is of course December. More information about this is available under Calendar Issues on the left-hand menu.
St. Clement of Alexandria (c.192 - 202)
"And our Lord was born in the twenty-eighth year, when first the census was ordered to be taken in the reign of Augustus." "And there are those who have determined not only the year of our Lord's birth, but also the day; and they say that it took place in the twenty-eighth year of Augustus, and in the twenty-fifth day of Pachon.... others say that He was born on the twenty-fourth or twenty-fifth of Pharmuthi." (The Stromata, Book 1, Chapter XXI)
Both dates agree upon the twenty-fifth (25th) or the eve thereof. This concurs with the historical view that Christ was born at midnight. The former date would be around late May; however Pachon was the ninth (9th) month of the calendar in use in Egypt at that time (Ideler. Chron., II, 397, n). It equates to Bashans in the Coptic calendar still in use today (see http://en.wikipedia.org/wiki/Pashons). For why this is important, please see the first quote on this page and look under Calendar Issues for further information. The latter date would be one month earlier. This can be explained by the fact that the Egyptian calendar has twelve (12) months plus five or six (5-6) extra days known as the epagomenal or intercalendary days. This time is also called "Pi Kogi Enavot" (ie "the little month") or "El Nasii". These days were usually counted as part of the previous season however it is not entirely unreasonable to see why the "others" referred to may have included these days as a first month in their calculations. Many speculative reasons for this could be given such as the annual flooding of the Nile coming earlier than expected or perhaps these "others" were foreigners. Regardless, St. Clement mentions it only secondarily anyway. Notably a similar form of confussion arises from the fact that "Dec"-ember (meaning 10) is the ninth month of the Julian Calendar! For why this is please see Calendar Issues. Josephus confirms the time of the year by referring to "the month Xanthicus... called by the Egyptians Pharmuth, and Nisan by the Hebrews; but the Macedonians call it Xanthicus" (The Antiquities of the Jews, Chapter 14, section 6 [or part 311 in the Greek text])
St. Justin Martyr (c. 110 - 165)
"Now there is a village in the land of the Jews, thirty-five stadia from Jerusalem, in which Jesus Christ was born, as you can ascertain also from the registers of the taxing made under Cyrenius, your first procurator in Judæa." (The First Apology of St. Justin Martyr, ch. XXXIV)
St. Justin appeals to the tax records as proof of Christ's birth.
Tertullian (145 - 220) likewise refers to:
"His enrolment in the census of Augustus—that most faithful witness of the Lord's nativity, kept in the archives of Rome" (Tertullian Against Marcion, Book IV, ch. VII)
As with most official records in the Roman world, the tax/census records were kept in Rome.
Elsewhere, Tertullian goes to great lengths to show:
"the day of the birth of Christ". (An Answer to the Jews, ch. VIII)
Although Tertullian focuses on the year, he determines the month also but does not state plainly the name of the month. Without knowing exactly the time of year when Daniel the Prophet received his vision about the 70 Weeks, it is not possible to determine the month intended. Nonetheless, this shows that Tertullian at least thought he knew the day of Christ's birth. Tertullian also makes numerous other references to the Lord's birth but these seem to be the clearest regarding the date thereof.
St. John Chrysostom (c. 380s)
"I have been looking forward to this day for a long time. It is only ten years ago that we became aware of the precise day of this solemnity; but thanks to your zeal, here we are celebrating it with as much excitement as if we had known about it for many a long year. The peoples of the East, from Thrace to Gadesh, have known about it for much longer." "All we have done is to refer in this matter to the testimony of people who possess an exact knowledge of it, and who lived in Rome; it is through the faithful in Rome that this information has been passed down to us." (Monitum in Hom. de Natal. Christi - Need Ref. in English please? Contact: Discussions & Research if you are aware of one please.)
Ironically, this is the passage which Hislop partially quotes to argue against the celebration of Christmas! Yet Hislop does not quote the parts which make it clear that St. John Chrysostom is convinced that this date is correct. He merely selectively quotes the small section supporting his preconceived ideas in a similar way to how certain cults do likewise today. Sadly, thousands of people have been tricked by this act of biased scholarship. It is always important to consider the context wherein a statement is made lest the reader gain a false impression of the intent of the author. What this quote in fact shows is that once peace had come and Christians were no longer persecuted, the true date of Christ's birth could be made known to all freely and gladly without fear. It is about this time when frequent mentionings of the date of Christ's birth begin to be made such as those shown below:
St. Ephraim the Syrian (Syrus) {known as The Lyre [Harp] of the East for his beautiful hymns} (c.306 - 373)
"In March when the lambs bleat in the wilderness, into the Womb the Paschal Lamb entered!" (Hymns on the Nativity, Hymn III)
"...being in the womb nine months for us..." (Hymns on the Nativity, Hymn IV)
"His conception was in Nisan, and His Birth in Conun." (Hymns on the Nativity, Hymn XV, v.6)
As is well known, Nisan aligns with late March and continues into April. When Conun falls should then seem clear even without a calendar to explain the matter. Do you have when Conun is? If you have knowledge of the ancient Syrian calendar used by St. Ephraim, please contact Discussions & Research
"To-day was born the Child, and His name was called Wonder! For a wonder it is that God as a Babe should show Himself." (Hymns on the Nativity, Hymn I)
"The staff of Aaron, it budded, and the dry wood yielded fruit! Its mystery is cleared up to-day, for the virgin womb a Child hath borne!" (Hymns on the Nativity, Hymn I)
St. Ephraim's first Hymn on the Nativity (Hymn I) repeatedly refers to "to-day", the day of the celebration of Christ's birth, as being the very day itself upon which He was born!
"He was born there who in writing should tell the Gentiles' number! The Psalm that David once sand, by its fulfilment came to-day!" (Hymns on the Nativity, Hymn I)
Commentators agree that this refers to Psalm 86 in the LXX (or 87 in the Hebrew).
Sulpitius Severus (c.363 - 420)
"Under this Herod, in the thirty-third year of his reign, Christ was born on the twenty-fifth of December in the consulship of Sabinus and Rufinus." (The Sacred History of Sulpitius Severus, Book 2, Chapter XXVII)
St. Bede the Venerable (c. 672 - 735) recalls pagan customs on the same date without insulting the Lord's birthday:
"...the ancient peoples of the Angli began the year on the 25th of December when we now celebrate the birthday of the Lord; and the very night which is now so holy to us, they called in their tongue modranecht (modra niht), that is, the mothers' night, by reason we suspect of the ceremonies which in that night-long vigil they performed." (De temp. rat. ch. 13 - Need Ref. in English please? Contact: Discussions & Research if you are aware of one please.)