Some guitars have the production date etched or stamped on the back of the guitar while others are marked with a serial number that indicates the production year. The serial number can be looked up on the guitar manufacturer's website to find out the year it was made.
Sometimes, there is a manufacturing date marked on the back of the guitar, such as on the neck block, back of the headstock or the back vibrato cover plate. However, this date often refers only to the date that the neck was made rather than the entire instrument. Most guitars are etched with a 10-digit serial number, which either conveys the production year or can be looked up online.