Why Are There Time Zones?

Article by: David Else, November 2007

The equinox has passed. In the northern hemisphere, days are getting shorter, in the south they're getting longer, and in both people are twiddling to reset their alarm clocks. Australians and Americans adjust for 'Daylight Saving', while Brits switch to the quaint-sounding 'Greenwich Mean Time' from the optimistically-titled 'British Summer Time'. Across the hemispheres you can hear the gentle chant of 'spring forward, fall back'.

While losing or gaining an hour can be disruptive, long-distance travellers make even greater leaps in time. Fly around the world in an easterly direction, say, from Paris to Singapore, and you're ahead by 8 hours; go west and you turn back time, arriving in New York before you left London.

The best time-warp trip involves crossing the Pacific - and the International Date Line. Last time I took this route was when I had an early morning flight from Melbourne, Australia to California, via New Zealand. I checked in then had some breakfast. The plane took off about 7am, and the passengers were served breakfast. When we landed in Auckland it was still morning, so we had breakfast. Then we took off and the first in-flight meal was - yep - breakfast. We landed in San Francisco around 7am local time. I'd arranged to meet friends near the airport, and we went to a nearby diner for - you guessed it - breakfast.

But what are these time zones exactly, and how do they fit in with the real world?

In the remote Namibian town of Katima Mulio, locals have taken time zones into their own hands.

In theory, each time zone relates to 15 degrees of longitude on the earth's surface, which the sun takes an hour to cross. The key line of longitude is zero degrees, known as the Greenwich Meridian; it was established in 1675 by mathematicians at the Royal Observatory in Greenwich, London. From here we get Greenwich Mean Time (GMT), although the official term is now Universal Time Coordinate. Today, Greenwich has a museum where visitors love to straddle the line - a long metal strip running through the museum courtyard - that separates western and eastern hemispheres.

There are 39 time zones across the world. A random number, admittedly, but there's a reason. Extra time zones exist because the difference between neighbouring countries is not always an hourly increment. Wedged between are half-hour and even quarter-hour differences - known as 'off-set' time zones. For example, Iran is 30 minutes ahead of Iraq.

The greatest time difference between two countries is three and a half hours, where China and Afghanistan share a tiny strip of border. At the other end of the scale, there’s a college in Oxford, England, where the clocks are set five minutes behind GMT. Oxford is 50 miles west of London, the reasoning goes, so naturally time is a little behind the capital. Or is this just a way to give students an excuse to be late for lectures?

In the remote Namibian town of Katima Mulio, locals have taken time zones into their own hands. The town is so far from the capital of Windhoek that locals have mostly abandoned the country's official time and adopted neighbouring Zambia's instead. A few diehards remain though, so when you're making dinner plans in Katima Mulio it's always best to check: 'Namibia time or Zambia time?'

I was stranded all night in no-mans-land with no idea exactly what time it was.

Elsewhere in Africa, the Malawi-Tanzania border presents another anomaly. On a trans-continental trip a few years ago, I was crossing here late in the afternoon. The guard-posts were a mile or so apart, and both closed at 5pm. But I forgot the one-hour time difference. So the Malawian officials cheerfully stamped my passport and waved me off at about 4.20pm, but when I reached the Tanzanian guard-post it was 5.30pm local time, and the guys in uniform had closed their office. I tried to negotiate, but they insisted I go back to Malawi, which I did, by which time that border gate had closed too, and I was stranded all night in no-mans-land with no idea exactly what time it was.

My favourite time zone story is another one from Africa. A rookie radio reporter in Ghana was given a script just moments before going live. He commenced his bulletin with 'It is now three o'clock Greenwich. Meantime, here is the news.'