From John Mark Minisitries
The current dating of the four Gospels, accepted by the biblical establishment, which includes scholars of every persuasion, is: Mark 65-70; Matthew and Luke in the 80s; John in the 90s. These dates are repeated by the columnists who write in our Catholic newspapers and the experts who draw up the curricula for religious education in our Catholic schools.
From suite 101
Jesus was crucified no earlier than AD 30 (probably AD 33) and everyone agrees that all four of the canonical Gospels were written after Jesus’ crucifixion. Thus, we can rest assured that the Synoptics (as well as the Gospel of John) were written no earlier than AD 30. Indeed, it is universally accepted that they were written well after the mid-30s AD.
The outer limit dates vary from Gospel to Gospel. The earliest external reference to the Gospel of Mark is Papias, dated to AD 130. Ignatius, the Bishop of Antioch, makes indirect references to Matthew as early as AD 110. This implies rather strongly that Matthew was in circulation by that year. Since the author of Matthew apparently utilized the Gospel of Mark, this would indicate that Mark was also in circulation prior to AD 110. Accordingly, we can conclude that Matthew and Mark were both compiled (in their present form) and in circulation prior to AD 110.
From New Advent
While the ancient lists, versions, and ecclesiastical writers agree in admitting the canonical character of only four Gospels, they are far from being at one with regard to the order of these sacred records of Christ's words and deeds. In early Christian literature, the canonical Gospels are given in no less than eight orders, besides the one (St. Matthew, St. Mark, St. Luke, St. John) with which we are familiar. The variations bear chiefly on the place given to St. John, then, secondarily, on the respective positions of St. Mark and St. Luke. St. John passes from the fourth place to the third to the second, or even to the first. As regards St. Luke and St. Mark, St. Luke's Gospel is often placed first, doubtless as being the longer of the two, but at times also second, perhaps to bring it in immediate connexion with the Acts, which are traditionally ascribed to the author of our Third Gospel.
Of these various orders, the one which St. Jerome embodied in the Latin Vulgate, whence it passed into our modern translations, and even into the Greek editions of the New Testament, is unquestionably the most ancient. It is found in the Canon of Muratori, in St. Irenæus, in St. Gregory of Nazianzus, in St. Athanasius, in the lists of the sacred books drawn up by the Councils of Laodicea and of Carthage, and also in the oldest Greek uncial Manuscripts.: the Vatican, the Sinaitic, and the Alexandrine. Its origin is best accounted for by the supposition that whoever formed the Gospel collection wished to arrange the Gospels in accordance with the respective date which tradition assigned to their composition. Thus, the first place was given to St. Matthew's Gospel, because a very early tradition described the work as originally written in Hebrew, that is, in the Aramaic language of Palestine. This, it was thought, proved that it had been composed for the Jewish believers in the Holy Land, at a date when the Apostles had not yet started to preach the glad tidings of salvation outside of Palestine, so that it must be prior to the other Gospels written in Greek and for converts in Greek-speaking countries. In like manner, it is clear that St. John's Gospel was assigned the last place, because tradition at a very early date looked upon it as the last in the order of time. As to St. Mark and St. Luke, tradition ever spoke of them as posterior to St. Matthew and anterior to St. John, so that their Gospels were naturally placed between those of St. Matthew and St. John. In this way, as it seems, was obtained the present general order of the Gospels in which we find, at the beginning, an Apostle as author; at the end, the other Apostle; between the two, those who have to derive their authority from Apostles.
The numerous orders which are different from the one most ancient and most generally received can easily be explained by the fact that after the formation of the collection in which the four Gospels were for the first time united, these writings continued to be diffused, all four separately, in the various Churches, and might thus be found differently placed in the collections designed for public reading. It is likewise easy in most cases to make out the special reason for which a particular grouping of the four Gospels was adopted. The very ancient order, for instance, which places the two Apostles (St. Matthew, St. John) before the two disciples of Apostles (St. Mark, St. Luke) may be easily accounted for by the desire of paying a special honour to the Apostolic dignity. Again, such an ancient order as Matthew, Mark, John, Luke, bespeaks the intention of coupling each Apostle with an Apostolic assistant, and perhaps also that of bringing St. Luke nearer to the Acts, etc.