well i cant driectly answer your question but i can tell you what i know. In order to get energy your body takes carbon and puts it through a cycle and oxidizes it for energy. in other words, the food you eat is taken in and converted to energy. The cycle for converting food to energy is called the Tricarboxylic acid cycle(TCA). This cycle accepts carbohydrates/protein/fat/ethanol. The food you eat is converted chemically into the precursors of this TCA cycle through pathways ill leave out(metabolism). Alcohol (ethanol) can be readily used in the TCA cycle and will be used instead of carbs/protein/fat because it is an easier source of energy(does not require much if any chemical manipulation).
so, from a common sense perspective: when all the ethanol in your body is used up. I would assume this is not too long after you are hungover. maybe close to a day or so depending on how much you drink of course. (still some time after the ethanol is used or excreted before cycles go back to normal)