David,
The first number of the code stamped on the label is the month packaged; the next 2 digits are the year packaged; the next 2 digits are the batch number used by the manufacturer. The expiration date is 4 years from the date packaged if the bottle is sealed. If the bottle has been opened, it is only good for 1 year. This info is straight from WPC brands (manufacturer). Hope this helps.
George