When buying a new automobile battery, how old a battery (according to the manufacture date) would be acceptable?
There is a difference between the date of manufacture and the date a battery is put into service. Many batteries are supplied “dry charged” as this reduces the weight ie no liquid. This is done to reduce transport costs...
Then, they are filled with acid / water mix at the correct concentration and can be used directly or given a “topping up “ charge if necessary.