As is the case with most modern car batteries, Bosch car batteries last many years before they need refurbishing or replacing. However, the problem lead-acid batteries suffer from is they provide little warning before they start dying. Your Bosch car battery may work fine all year, and then you may get one very cold night and go to start your car and the battery is dead. It's sensible to check how old your Bosch car battery is so you can consider a replacement.
Put on protective gloves before you check out your Bosch battery. You're likely to get dirty and you may touch the battery terminals.
Open your car's bonnet and locate the Bosch battery.
Look at the top of the battery or on the battery terminal. There is either an indelible stamped mark or a label indicating the year of manufacture.
Read the stamped mark or label. It usually has numbers. The first two numbers are the month it was made and the last two or four digits signify the year. For example, if it says 091999 it means September 1999, or if it says 0109 it means January 2009. Sometimes it has other numbers such as serial numbers after, or before the date. Some batteries have a code starting with a letter and followed by a number. A battery with a code A09 for example means January 2009.
Check if your Bosch battery is out of date. Some, but not all, batteries show the expiration date. This is the date after which it should not be sold. It starts with Ex or Expires, followed by the date. If the expiration date has long passed -- by two or three years -- it may be worth getting a replacement.