How much time does it take for alcohol to damage the liver?

How badly? You can give yourself fatty liver over a single wild weekend. It'll heal right up soon after the hangover. For cirrhosis, the traditional wisdom is 15 pint/year of the hard stuff (say, 3 pints of whiskey a day for five years) to have any chance of cirrhosis. Alcoholic hepatitis usually follows going on a drunk sometimes after sobering up. Please use alcohol wisely if at all.