St. Justin martyr lived in the 2nd century. he describes the (Greek language) litrugy in Rome in the middle of the 2nd century.
the earliest Divine Liturgy is believed that of +James (the Just) of Jerusalem. Orthodox liturgies from the 4th cen 5th century (+Basil's and +Chrysostom's) are very much related and an obvious outgrowth of the original.
Lack of original liturgical text makes it difficult to date. It is known, however, that in the 3rd century it was brought into conformity with the trinitarian doctrine of the Church. It contains lots of readings ansd references to the OT (the reason being is tha, it is speculated, at the time it was written the New Testament hasn't been written yet), which would place it around the middle of the 1st century. Others date is much later (3rd century).
Nonetheless, the description of St. Justin Martyr shows that the Euchairstic nature of the divine service was known to the Church from the earliest roots.
This is further corroborated by Didache (c. 70 AD), so much so that together with the DL of +James there is plenty of evidence that the liturgical life of the Church existed from the earliest days and was concentrated on the Eucharistic Real Presence.
The first occurrence of the Didache was 1873.
I stand corrected. I was going from memory. :)