Early Christian Writings - The Didache - 120AD

“Granting the general authenticity of the Greek work, the time of composition must be at least as early as the first half of the second century. If the Teaching is older than Barnabas, then it cannot be later than A.D. 120. If both are from a common source, the interval of time was probably not very great. The document itself bears many marks of an early date…”
(Anti-Nicene Fathers, Vol 7. pp. 374-375).
St. Athanasius the Great (d. 373) seems to have recommended this work in his 39th Easter Epistle : “But for greater exactness I add this also, writing of necessity; that there are other books besides these not indeed included in the Canon, but appointed by the Fathers to be read by those who newly join us, and who wish for instruction in the word of godliness. The Wisdom of Solomon, and the Wisdom of Sirach, and Esther, and Judith, and Tobit, and that which is called the Teaching of Apostles, and the Shepherd.”
(Nicene and Post-Nicene Fathers, 2nd Series, Vol. 4, p. 552, italics added)
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*Interestingly the Didache provides evidence of people with the gift of speaking in tongues right up to the 120AD. The liturgical description of Baptism is also provided, in which the Orthodox Church correctly maintains full immersion.