It should have a date stamp on the top of the battery there be little numbers like 04 05 06 07 08 09 but sometimes there isn't if its factory there prob isn't did you buy the car new are used
How To Know If My Car Battery Is Old?
The only real way to know is to test the battery. Have the battery fully charged and then see what the voltage is. It should be a bit higher then 12.5. Any lower and your battery is bad.
In general if the battery is beyond its warranty period you should consider replacing it.
In general if the battery is beyond its warranty period you should consider replacing it.