How much time elapsed between the original writing and the earliest copy we have available today? A longer time span since the original would mean more generations of copies, thus more room for human error. Most of the early copies we have of New Testament documents date to within 90 years of the original; some may be closer than 20 years.
Until recently a fragment of the Gospel of John, dated about 125 AD, was the earliest known copy of any part of the New Testament. In 1972, however, nine New Testament manuscript fragments were found in the caves near the Dead Sea. Among these were part of Mark dated about 50 AD, part of Luke dated about 57 AD, and part of Acts from 66 AD. Remarkably, this places these copies not more than a decade or two (and perhaps only a few years) from the original documents.
Additionally, complete New Testament manuscripts have been found, such as Codex Vaticanus and Codex Sinaiticus, which are dated to 325-50 AD and 350 AD respectively. Compare this to the earliest copies of Sophocles' writings dated 1400 years after the original.
The next page provides a summary of the Bibliographic Evidence Test of the New Testament as compared to several other documents or similar antiquity.