The first place to look is on the top of your battery’s case. You’ll see a four-digit code stamped on the cover or printed on a sticker. The first two characters of this code indicate when the battery was shipped from the factory to the distributor. The letter at the beginning refers to the month — A for January, B for February, etc. The number that follows refers to the year. For example, 9 for 2009 and 1 for 2011.
Keep in mind that car batteries usually last three to six years. If you start to notice your battery case being swollen, a sulfuric rotten egg smell coming from the battery, or hesitation on starting, it might be time to start looking at getting a car battery replacement done.