Note: it has been suggested that, from that verse (47:6), the word "ancient" would indicate the epistle was written in the 2nd century:
"It is shameful, dearly beloved, yes, utterly shameful and unworthy of your conduct in Christ, that it should be reported that the very steadfast and ancient Church of the Corinthians, for the sake of one or two persons, makes sedition against its presbyters."
But "ancient" is vague & not descriptive about a number of years, and, in no way, would imply the Church of Corinth was created many decades before the letter was written. "Clement" probably suggested by "steadfast and ancient" the church of Corinth was too mature to get into this (infantile) bickering.
According to the above, a dating around 80-85 would be warranted. "However, most scholars contend that '1 Clement' was written in 96, right after Domitian's persecution. The evidence they cite is solely from a sentence in ch. 1:
"Owing, dear brethren [the Corinthians], to the sudden and successive calamitous events which have happened to ourselves [the Christians of Rome], we feel that we have been somewhat tardy in turning our attention to the points respecting which you consulted us"
But any persecution under Domitian (93-96) could hardly be referred as "sudden and successive calamitous events". Furthermore, Domitian's persecutions (supported from scanty evidence) were not momentous in Rome itself (and not even necessarily against Christians!).
However here, the calamities appear to be local: "...events which have happened to ourselves".
But if Domitian's persecution is not the events alluded to, do we have a record of successive calamities afflicting the Romans prior to 96?
The answer is YES.
Suetonius: De Vita Caesarum--Divus Titus, c. 110:
"There were some dreadful disasters during his reign [Titus], such as the eruption of Mount Vesuvius in Campania [August 79], a fire at Rome which continued three days and as many nights , and a plague the like of which had hardly ever been known before . In these many great calamities ..."
Note: the plague affected Rome and most of Italy, but not the rest of the empire.
2) Dating through the external evidence:
Because the dating of the gospels is rather complicated, I asked my readers, if interested, to consult my website for explanations, starting here. For only gMark, see here. For only gMatthew, see here. For only gLuke, see here.
My conclusions are 81-93 for gLuke and 81-93 for gMatthew, which is close to the near-concensus of critical scholars.
A) Did the author of '1 Clement' know about gLuke or/and gMatthew?
Considering, in '1 Clement',
a) Jesus is never described as a descendant of David (he is "demonstrated" NOT one in Mk 12:35-37), but will be many times in the two later Synoptics.
b) there is no hint about a virgin conception (as in Mt 1 and Lk 1). Instead Jesus is described as a descendant of Jacob "according to the flesh" as for "priests and all the Levites" and "kings, princes, and rulers of the race of Judah" (ch. 32).
From these observations, it is not likely "Clement" knew about the later gospels.
Note: on this webpage, I explained "Clement" utilized gMark & 'Hebrews'.
B) Did the author of gLuke know about '1 Clement'?
Let's look at the following:
a) Lk 6:36-38 NASB "Be merciful, just as your Father is merciful. Do not judge, and you will not be judged; and do not condemn, and you will not be condemned; pardon, and you will be pardoned. Give, and it will be given to you. They will pour into your lap a good measure pressed down, shaken together, and running over. For by your standard of measure it will be measured to you in return.''
Let's notice the "give" clause is only in gLuke & '1 Clement' (& not in any other gospel).
b) 1 Clement, ch. 27 "for nothing is impossible with God"
Lk 1:37 NASB "[the angel Gabriel to Mary] For nothing will be impossible with God."
The expression "(nothing) ... impossible with God" appears only here in all the NT.
c) 1 Clement, ch. 48 "make straight their way in holiness and righteousness ['en hosiotati kai dikaiosuna']"
Lk 1:75 "... serve Him without fear, in holiness and righteousness ['en hosiotati kai dikaiosuna'] ..."
The expression "holiness and righteousness" appears only here in all the NT.
In conclusion, it is probable "Luke" knew about '1 Clement'.
Note: I explained here "Luke" did not know about Josephus' Antiquities (published 93).
C) Did the author of 'Acts' ("Luke") know about '1 Clement'?
a) 1 Clement, ch. 18 "... God said 'I have found a man after my own heart, David the son of Jesse; and in everlasting mercy have I anointed him?'"
The closest O.T. passages are Psalm 89:20
"[God saying] I have found my servant David with My holy oil I have anointed him"
and 1 Samuel 13:14 LXX
"[Samuel says] the Lord shall seek for himself a man after his own heart"
Let's notice the conflation, a specialty of "Clement"!
And in 'Acts', we have:
Ac 13:22 "... [as testified by God] I have found David son of Jesse, a man after my own heart, who will do all My will."
Who copied whom?
In '1 Clement', David is named four times but never as "servant" (however Moses is declared God's servant four times!). But "Luke" did not have a problem with "servant David", which appears in Lk 1:69 & Ac 4:25. And if "Luke" copied from Psalm 80:20, there was no reason to drop "my servant", more so because it fits "who will do all My will". All of that suggests strongly "Luke" used '1 Clement', and NOT vice versa. Furthermore, "Clement" had to know about Psalm 89:20, because he obviously extracted "I ... anointed him" from it. But "Luke" needed only '1 Clement' when writing Ac 13:22!
b) 1 Clement, ch. 2 "And you were all humble-minded and in no wise arrogant, yielding subjection rather than demanding it, giving more gladly than receiving"
Let's notice "Clement" did not introduce the words in bold as being from Jesus. But "Luke" did embellish, as it seems:
Ac 20:35 "... Jesus Himself said, 'It is more blessed to give than to receive.'"
In conclusion, "Luke" likely knew about '1 Clement' when writing the gospel and 'Acts'.
A reminder: I explained here "Luke" did not know about Josephus' Antiquities (published 93) when writing 'Acts'.
D) Did the author of gMatthew know about '1 Clement'?
Let's look at these items:
a) Mt 5:7 NASB "Blessed are the merciful, for they shall receive mercy."
The Greek root for "merciful" ('eleemon') is the same in '1 Clement' and here, but different in Lk 6:36-38 ('oiktirmon').
Also gMatthew is closer to '1 Clement' ("Be merciful, that you may obtain mercy") than gLuke ("Be merciful, just as your Father is merciful").
b) Mt 7:1-2a NASB "Do not judge so that you will not be judged. For in the way you judge, you will be judged ..."
This first sentence is almost word by word as in Lk 6:37 ("Do not judge, and you will not be judged") but again differing from '1 Clement' ("as you judge, so shall you be judged"). However, the second one is very similar to the one by "Clement".
And it appears we have a contradiction here: first "do not judge", then "as you judge"! It seems "Matthew" combined the two versions, that is the one from "Q" and the one from '1 Clement' (as he did in 13:31-32 (parable of the mustard seed, again introducing conflicts) and 12:31-32, combining the "Q" version with Mark's).
In conclusion, it is probable "Matthew" knew about '1 Clement'.
Note: I explained here gMatthew was written before 93.