How do you know if you have chronic hepatitis instead of acute?

it depend upon the health of your immune system
because  viral infections can often re-occur if you are run down by bad diet or another different infection

the problem really is if your liver is so damaged that it is only borderline functional and you overstress it with say bad diet and you cause a vicious cycle leading to the top paragraph

Longer than 6 months is the cutoff that separates acute from chronic hepatitis. Hepatitis A does not cause chronic hepatitis. One either resolves the infection or in rare instances can die from it. The others mentioned are capable of causing chronic hepatitis with HCV causing a greatly increased rate of chronic hepatitis vs hepatitis B in adults. When infants and young children are exposed to hepatitis B about 90% develop chronic infections and later exposures as an adult tend to have more people resolve the infection without developing chronic hepatitis.