February 23, 1455
While maybe not exactly accurate, February 23rd, 1455 is generally accepted as the date that the Gutenberg Bible was first published. This was the first book on record to be printed on movable type. Until that point, books were copied by hand, which was obviously a slow, laborious process.
On a side note, I challenge anyone to come up with a historical date in technology earlier than this one! Good luck!