[anigbrowl]

With a single timezone then you need to know the longitude of the remote location instead. There's a book (called Longitude, unsurprisingly) about the piecewise invention of accurate chronometry in order to solve the problem of knowing your longitude at sea. Latitude you can work out pretty easily as long as you have an almanac, compass, and a protractor, but longitude is a problems sans clocks and logs of distance traveled.