Two friends, whom we will call Arthur and Robert, were curators at the Museum of American History. Both were born in the month of May, one in 1932 and the other a year later.

Each was in charge of a beautiful antique clock. Both of the clocks worked pretty well, considering their ages, but one of them lost ten seconds an hour and the other gained ten seconds an hour.

On one bright day in January, the two friends set both clocks right at exactly 12 noon.

``You realize,'' said Arthur, ``that the clocks will start drifting apart, and they won't be together again until---let's see---why, on the very day you will be 47 years old. Am I right?''

Robert then made a short calculation. ``That's right!'' he said.

Who is older, Arthur or Robert?