OK, I have one today that requires your full thinking cap application. Ready for it?
The only timepiece that Mr. Greenwich owns is a grandfather clock which he frequently forgets to wind. One day when this happened, he went to Mr. Terminal's house to check the time. When Mr. Greenwich returned home, the first thing he did was set his grandfather clock to the correct time. How could he correctly set his clock if he did not know the length of the trip to Mr. Terminal's house? Note: Before you ask, no, he did not use a radio, telephone, or any other sort of communications or broadcast device to aid him, nor did he lug the grandfather clock to Mr. Terminal's house and back.