Goodbye summertime

So daylight savings is over for another year. Back to boring old standard time.

Now’s a good moment to comment on what time zone New Zealand sits in. In ‘winter time’ it sits twelve hours ahead of Greenwich Mean Time, GMT (or Univeral Time, as astronomers like to call it). Is that reasonable?

In Greenwich (south-east London), in GMT, the sun reaches its highest point in the sky at 12 noon (give or take a few minutes depending on time of year – see my comment on the equation of time and analemma). Does it do the same in NZ?

The Greenwich meridian, 0 degrees longitude, runs through Greenwich. Therefore, for a time zone 12 hours ahead of Greenwich, we’d expect the sun to hit peak elevation at noon for locations with longitudes 180 east (or 180 west for that matter). NZ isn’t quite that far east, but it’s pretty close. East Cape sits about 178 and a half degrees east, while the western tip of Fiordland is about 166 and a half.

That means NZ’s choice of time-zone makes sense – its the best ‘whole number’ time zone we could have. (Some places, like South Australia, go in for half time-zones, just to confuse everyone, but let’s not go there.) Those living in the deep south might justifiably disagree here – their western-ness means, for example, sunrise is pretty late in winter. However, splitting a small country into two zones is a bit silly, and the one it is in suits the large majority of its population.  

(I should add the Chatam Islands, for reasons best known to themselves, are three-quarters of an hour ahead of the rest of NZ. Just why I can’t figure out – maybe someone can enlighten me.)

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