How can a battery be bad if it's less than a year old.

Have it load tested to find out if its good

Sometimes it just happens. There can be a bad bad of materials that go into them such as lead. They might get prepped improperly, meaning they arrive dry to distributor and acid is added and then they get their first charge.
One thing that will get to batteries is quick discharges and quick charges.
This is like having your battery drain quickly due to a short or the lights being left on all night. That is a quick dis-charge. A quick charge is a jump start or charging using a qucik charger.
That is why cheap battery chargers are just that, cheap. Trickle chargers which slowly charge a battery and do it using the properly conditioned charge cycle and pahse cost a lot of money. The newer dry cell gel batteries actually require a special charger designed just for them. They can fail early too, as one went out on me in less than two years and it was a TEN year battery, even when they cost $200+.
Cars can just be a pain sometimes. That's why we are here. To help you out and ease the pain a little if we can.
I hope the information helps. You are not alone in this happening.

They will pro-rate the refund or credit towards new battery. That means they will take off money for the time that you have had battery.
Bikes are okay, but they suck in the rain. Cars get frustrating at times but it will pass and you are not dealing with the worst case of car pain I have heard. You are certainly not alone as I myself have suffered through countless cars and been in similar situations with batteries that were never supposed to fail. Nothing is perfect, but a car is nice to have when it is working right.
Hang in there.