half-your-age-plus-seven

The social rule defining the youngest age one may date without it being socially unacceptable (or illegal). To compute the oldest one could date without it being socially awkward, simply subtract seven from one's own age, and multiply by two. To compute the acceptable age an otherwise inappropriately matched couple would have to be before they could date, find the difference in their age, multiply by two, and add seven to get the age the older partner would have to be. And remember, always round up when computing the youngest age you can date, and round down for the oldest. You know, just to be on the safe side.