There is often much confusion about the hour differences between countries. Time zones for differing countries are based on either, Universal Coordinated Time (UTC) or Greenwich Mean Time, (GMT).

Universal Coordinated Time and Greenwich Time are essentially the same, except that  UTC is also based on International Atomic Time (TAI), but unless you are interested in counting time in milliseconds or less, then world time zones are based on UTC or GMT.

Differing countries base their local time on the number of hours either in advance, or behind UTC or GMT, usually an integral number. For example GMT or UTC + 8 means the location is 8 hours in advance, or GMT/UTC – 8 indicates the location to be 8 hours behind the standard time.

Not all countries use an integral number to indicate their time offset from the standards of UTC or GMT. What follows are a few examples of differing time offsets.

Countries not using an Integral Number as Offsets from GMT/UTC.

-          Canada (Newfoundland) is GMT/UTC -3hr. 30min.

-          India is GMT/UTC + 5hr. 30min.

-          Australia (North and South Territories) are both GMT/UTC + 9hr. 30min.

-          Lord Howe Island (Australia) is GMT/UTC + 10hr. 30min

-          Norfolk Island (Australia) is GMT/UTC + 11hr. 30min.

-          Afghanistan is GMT/UTC + 4hr 30min.

For some reason there are countries which choose to be offset from GMT/UTC by one quarter hour and not a full integral number. –

Countries using One Quarter Hour Offset from GMT/UTC.

-          Chatham Island (New Zealand) is GMT/UTC + 12hr. 45min.

-          Nepal is GMT/UTC + 5hr. 45min.

Many countries will alter their clocks to ‘gain’ an extra hour of daylight in summer time. For instance, in winter time in the United Kingdom GMT/UTC 0.00hr. The Philippines is GMT/UTC + 8hr. But during UK summertime, the UK change their clocks, and the time difference between the two countries becomes Philippines GMT/UTC + 7hr. This time changing is referred to as Daylight Saving Time (DST).

There are many anomalies associated with time zones. The small Pacific country of Kiribati had two different time zones. The eastern part was a full day and two hours behind the western part of the country. In 1995 adjustments were made to the International Date Line and now the entire country is within the same day. The situation today is –

-          Kiribati is GMT/UTC +12hr.

-          Phoenix Island is GMT/UTC + 13hr.

-          Christmas Island is GMT/UTC + 14hr.

Paradoxically, the adjustment to the International Date Line now means that although East Kiribati and the island group of Hawaii are both on the same longitude, their time zones are one day apart.

It is a fact, that despite having such standardized time procedures such as GMT and UTC, and we can tell the time atomically to the ‘nth’ degree by using Cesium clocks .There still exists much confusion, and many anomalies in the hours between countries.

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