Title: First Epistle of John
Content:   A Trinitarian gloss (marginal note) known as the Johannine Comma, added to Latin translations of the epistle in the 4th century, was interpolated (added to the main text) within 1 John 5:7-8 over the course of the Middle Ages. Although no Greek manuscripts before the 15th century include the passage, Erasmus added it to later editions of his edition of the New Testament, beginning in 1522. Bibles translated from his edition integrate the passage, including the King James Version (1611), which renders it as follows (in italics): "For there are three that beare record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. And there are three that beare witnesse in earth, the Spirit, and the Water, and the Blood, and these three agree in one." Translations made since the 18th century and based on a critical edition do not include this text, or include it as a footnote. Because the addition supports the doctrine of trinitarianism, it featured in Protestant and Catholic debates on this subject in the early modern period.
Title: Johannine Comma
Content:  The Epistle of Gregory, the Bishop of Sis, to Haitho c. 1270 utilized 1 John 5:7 in the context of the use of water in the mass. The Synod of Sis of 1307 expressly cited the verse, and deepened the relationship with Rome. Commentators generally see the Armenian text from the 13th century on as having been modified by the interaction with the Latin church and Bible, including the addition of the comma in some manuscripts.
Title: An Historical Account of Two Notable Corruptions of Scripture
Content:  sunt;" in another old copy the seventh verse was, but with interlining; in another much more modern copy, ver. 7 was also, but differently from the old copy; and in two other old manuscripts, also, ver. 7 was quite out, but as I remember in all of them the end of the eighth verse was 6 tres unum sunt.'" Newton's work also built upon the textual work of Richard Simon and his own research. The text was first published in English in 1754, 27 years after his death. The account claimed to review all the textual evidence available from ancient sources on two disputed Bible passages: 1 John 5:7 and 1 Timothy 3:16. Newton describes this letter as 
Title: An Historical Account of Two Notable Corruptions of Scripture
Content:  Newton concludes: "If the ancient churches in debating and deciding the greatest mysteries of religion, knew nothing of these two texts, I understand not, why we should be so fond of them now the debates are over." With minor exceptions, it was only in the nineteenth century that Bible translations appeared changing these passages. Modern versions of the Bible from the Critical Text usually omit the addition to 1 John 5:7, but some place it in a footnote, with a comment indicating that "it is not found in the earliest manuscripts". Modern translations of 1 Timothy 3:16 following the Critical Text now typically replace "God" with "He" or "He who", while the literal Emphasized has "who". A number of papers in the years following responded to Newton, notably John Berriman in 1741, who had seen at least some of Newton's text prior to publication. Later, Frederick Nolan in 1815, Ebenezer Henderson in 1830 and John William Burgon in the Revision Revised in 1883 all contributed substantially to the verse discussion.
Title: Novum Instrumentum omne
Content:  text lacked part of the 1 John 5:7-8 (Comma Johanneum). Erasmus replied that he had not found it in any Greek manuscript. Stunica answered that Latin manuscripts are more reliable than Greek. In 1520 Edward Lee accused Erasmus of tendencies toward Arianism and Pelagianism, and of unorthodox sacramentology. Erasmus replied that he had not found any Greek manuscript that contained these words, he answered that this was a case not of omission, but simply of non-addition. He showed that even some Latin manuscripts did not contain these words. Erasmus asked his friend, Paulus Bombasius, to check the Codex Vaticanus. Bombasius sent two extracts from this manuscript containing the beginnings of 1 John 4 and 5 (it did not include the Comma). The second edition became the basis for Luther's German translation.
Title: Johannine Comma
Content:  In the Tome of Leo, written to Archbishop Flavian of Constantinople, read at the Council of Chalcedon on 10 October 451 AD, and published in Greek, Leo the Great's usage of 1 John 5 has him moving in discourse from verse 6 to verse 8: "This is the victory which overcometh the world, even our faith"; and: "Who is he that overcometh the world, but he that believeth that Jesus is the Son of God? This is he that came by water and blood, even Jesus Christ; not by water only, but by water and blood; and it is the Spirit that beareth witness, because the Spirit is truth. For there are three that 
Title: John 7
Content:  500s (but displaying a form of text which has affinities with "Western" readings used in the 100s and 200s). Codex Bezae is also the earliest surviving Latin manuscript to contain it. Out of 23 Old Latin manuscripts of John 7-8, seventeen contain at least part of the pericope, and represent at least three transmission-streams in which it was included. The New King James Version includes the text with the explanation that the words from John 7:53 to 8:11 are bracketed by NU-Text "as not original. They are present in over 900 manuscripts of John" and the Jerusalem Bible claims "the author of this passage is not John".
Title: Johannine Comma
Content:  In 1 John 5:7-8 in the Received Text, the following words appear (the words in bold print are the words of the Johannine Comma). (Received Text) 1 John 5:7 … οἱ μαρτυροῦντες ἐν τῷ οὐρανῷ ὁ πατὴρ ὁ λόγος καὶ τὸ ἅγιον πνεῦμα … 8 … οἱ μαρτυροῦντες ἐν τῇ γῇ τὸ πνεῦμα καὶ τὸ ὕδωρ καὶ τὸ αἷμα … In 1 John 5:7-8 in the Critical Text and Majority Text, the following words appear. (Critical and Majority Text) 1 John 5:7 … οἱ μαρτυροῦντες 8 τὸ πνεῦμα καὶ τὸ ὕδωρ καὶ τὸ αἷμα … According to Johann Bengel, Eugenius Bulgaris, John Oxlee and Daniel Wallace, each article-participle phrase (οἱ μαρτυροῦντες) in 1 John 5:7-8 functions 
Title: Jesus and the woman taken in adultery
Content:  using exemplars from Egypt), the text is marked at the end of John chapter 7 with an "umlaut" in the margin, indicating that an alternative reading was known at this point.This codex also has an umlaut alongside blank space following the end of the Gospel of John, which may convey that whoever added the umlaut was aware of additional text following the end of John 21 – which is where the pericope adulterae is found in the f-1 group of manuscripts. Jerome, writing around 417, reports that the pericope adulterae was found in its usual place in "many Greek and 
Title: List of New Testament verses not included in modern English translations
Content:  several more in which the original scribe omitted it but a later hand inserted it. It is also missing from the Syriac and Sahidic versions and some Egyptian versions. The earliest Greek Codex showing this pericope at all is D (Codex Bezae), of the 5th or 6th century - but the text in D has conspicuous variants from the Textus Receptus/KJV version, and some Old Latin manuscripts no older than the 5th century, and many subsequent Greek and Latin mss all at the familiar location following John 7:52. The first Greek Church Father to mention the pericope in its familiar place 

Question: when was 1 john 5 7 added to the bible?
Answer: the 9th century.