Ask yourself: Is it noon?

• No? Wait until it is
• Yes? Proceed to next step

Consult your chronometer and learn what time it is in Greenwich, England

Calculate the difference between your time (noon or 12:00) and Greenwich time

Convert the difference in time into a difference in longitude:

1. For every FULL hour of time difference, figure 15° of longitudinal difference (so multiply every hour to the left of the colon by 15°)

2. For every FOUR minutes of time difference, figure 1° of longitudinal difference and add it to the answer in #1: Divide the minutes to the right of the colon by 4.

3. If your answer is not a round, whole degree number, turn the decimal answer into a fraction or into minutes and seconds (e.g., if your answer were, say, 29.75°, you'd report it as 29¾° or 29° 45')

Ask yourself: Is Greenwich time earlier than you or later than you? That is, does Greenwich have a smaller number than 12:00 or a larger number than 12:00?

• Greenwich is earlier than you
  • You are EAST of Greenwich, so add the suffix E to your answer
  • You are done

• Greenwich is later than you
  • You are WEST of Greenwich, so add the suffix W to your answer
  • You are done

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Last Updated: 01/28/02