The time recorded in places within the same longitude. A longitude is an imaginary line running from N to S which shows how far E or W a place is from the prime meridian.

Greenwich Meridian (0◦) longitude is the point of reference when calculating time. Time is gained towards the E and lost towards the W.

Examples

- Suppose the time at GWM is 12 noon what is the local time at Jos 40◦E?

Time gained=40×4=160min=2 hours 40min

Local time at Jos is 12.00+2.40=14.40-1200=2.40pm.

- At Dar-es-Salaam 40◦E time is 12pm what is the time at Ecuador 40◦E?

40◦+20◦=60◦

60×4=240min=4hours

Ecuador is behind in time =12.00-4=8 am.

If the places are on the same side subtract the degrees to get the difference and add or subtract from the reference time depending on which side the place is.

## Calculation of Longitude

What is the longitude of place x whose local time is 8 am when local time at GWM is noon? Time difference =12.00-8=4 hours Degrees=4×15=60◦ Since x is behind in time its then 60◦W.

## Standard Time and Zones

- Standard time is time recorded by countries within the same time zone.
- Standard time was come up with due to confusion resulting from time changing at every longitude.
- The world has 24 time zones.

The International Date Line It’s the 180◦ longitude.

## Effects of Crossing It

- One gains time when he crosses it from W to E and has to adjust the clock ahead by 24 hours.
- One loses time when he crosses it from E to W and has to adjust the clock backwards by 24 hours.