Batteries are only meant to have a shelf life of 1 year. The date code on them is usually a black sticker with white lettering. The first should be a letter and runs from A to L. January to December. A for January, B for February, etc. The last number is for the year, 4 for 2014, 5 for 2015. Etc. Once a batter hits 1 year from the date on the battery it is too be pulled and returned to the manufacturer. However in many circumstances this does not happen. Batteries are also supposed to be rotated, closest to the front of the shelf, closest to expiration. If its followed the fresher batteries are in the back.