I'm not sure what you mean by 'discovered' tbh. Time zones are an entirely man-made construct. The need for them arose during the 19th Century, when trains made travelling around countries much quicker than before, and so a kind of 'standard time' was needed to iron out more minute differences in longitude. For instance, noon in Bristol comes roughly 10 minutes after noon in London. In pre-industrial Britain, this did not make much of a difference to anyone's life, however having a slightly different time for every single town in Britain understandably made things like train timetabling rather difficult. Hence the need for time zones.