There are 17 hours difference in time zones between San Francisco and Tokyo. If an airplane leaves Tokyo at 3 p.m. on Friday, and flies 10 hours to San Francisco, what day and time does it arrive in SF? (don't forget to write am or pm and the day)

It might seem like a trick question, but it's possible for a flight to land at an earlier time on the same day it departed. This phenomenon often happens on trans-Pacific flights traveling eastward, from Asia to North America, because you cross the International Date Line. This imaginary line running through the Pacific Ocean marks the boundary where one calendar day officially ends and the next begins.

Let's break down the journey. The 10-hour flight departs from Tokyo at 3 p.m. on a Friday. If we simply add the flight time, the plane would land at 1 a.m. on Saturday in Tokyo's local time. This is the first step, calculating the arrival based on the departure city's clock.

However, San Francisco's time zone is a full 17 hours behind Tokyo's. To find the arrival time, we must subtract those 17 hours from the 1 a.m. Saturday arrival point. Counting backwards 17 hours from 1 a.m. Saturday brings us all the way back to 8 a.m. on Friday morning. The plane effectively travels "back in time (Review)," arriving on the same day it left.

This journey across the International Date Line is a classic example of how global travel can bend our perception of time. By flying east, against the Earth's rotation, passengers essentially "gain" a day on the clock, making what seems impossible a simple matter of geography and arithmetic.