6.5 years on a battery - new personal record!

Whenever I buy a new battery I try to get the latest date possible. Sometimes you don' t have the ability to rummage through them. I recently bought a battery from Sam' club on sale. I put the battery on the trickle charger and it read 12.6 volts. So over night the next day still read 12.6 volts. I thought maybe a problem with the battery but looked at the charger and saw it was on 6 volts. Switched to 12 Volts and then read 13.6 which is a full charge.