How old is my battery?

I believe battery date codes will need deciphering, if there's any from the manufacturer on the battery. Probably to avoid cherry picking? I would guestimate the battery's age is within 6 months of the car's 10/12 (October, 2012) manufacture date.

If you don't have one, pick up a digital multi meter (around $30~200), and read the battery's at-rest voltage. At the under-the-hood fuse box jumpstart point is fine. If it's 12.5 volts or higher your still fine.

Reading the voltage is a pretty rudimentary assessment. Better would be to hook a digital load tester , something like the prosumer level Solar BA5 (around $75). It'll tell you the voltage, plus the battery's actual Cold Cranking Amps (or Cranking Amps), and will give an assessment, either: ok, ok-but-charge, or fail. If you don't want to outlay for something like that, most competent retailers selling batteries should have a pro-level tester and will test your battery.

Four or five years is a sensible time to consider replacing the battery, regardless of it's condition. A little less, or a little more, depending on your mind set. It's always better to replace it at your convenience, than to be stuck and have to make snap decisions.

 

It's not really a matter of how old the battery is, it's how often you actually use the car to keep it charged up.

If you drive 30 minutes a day, your battery should have no issues for 5 years, to 2018

My daily driver still has the battery from 2008, still going strong

 

Yeah that's where we run into trouble; the car will is typically used only every other day, and there's often longer hiatus. As long as the battery's hooked up there's a small but constant phantom load. I'm cognizant of it, welcome occasional long runs, monitor the battery and periodically hook up a charger.

Was even thinking about a switch, that disconnects it, but that's disruptive, you lose all the trip meters, radio presets, maybe even auto-up on door windows needs retraining.