Calculating time differences

Now that we have a greater understanding of the Earth’s rotation and Australia’s position in relation to the prime meridians we can confidently calculate time differences around the world.

Open the Calculating Time Differences spreadsheet (.xlsx 12kB) and follow the instructions to determine the differences in time between major cities around the world.

To calculate the time difference between two positions use the formula:

Time difference = Angular difference x 4/60

where 1º corresponds to 4 minutes.

When entering this formula in the spreadsheet, we calculate the angular difference first:

= (cell ref1 – cell ref2)

Then in the time difference column:

=(angular difference)*4/60

+ or – Greenwich Mean Time

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Use the same calculations to determine the time differences of each city from Greenwich Mean Time in the Calculating Time to Greenwich Mean Time spreadsheet (.xlsx 13kB).

The most important aspect of this calculation is to determine whether the city is in front of or behind GMT. Look carefully at the longitude coordinate and Google Earth to calculate the position of each city in relation to the Greenwich Meridian.

Complete the spreadsheet and compare your results with the information on this link:

http://wwp.greenwichmeantime.com/world-clock/⁴