Crystal Reports: Time Zones

Greenwich Mean Time was established in 1675 to help mariners calculate longitude at sea. Research tells us that New Zealand was the first country to adopt a standard time for the entire country in 1868.

A painfully interesting twist on time zones is Daylight Wasting Time. Politicians call it "Daylight Savings Time," even though the clock shift wastes an hour of daylight at night, causes an extra hour of daylight each morning, and causes a spike in both traffic accidents and industrial injuries.

Fans of Ray Bradbury are familiar with the manipulative language technique of naming an undesirable program by an innocent-sounding or even positive name. In the interests of intellectual honesty, we will forego the politically correct name and call this bad and costly legislation by what it is.

Now that the UK can have DWT, the base for all time zones is called UTC (Coordinated Universal Time or Universal Time Coordinates) but is still based at Greenwich in London.

This is what you should store in your database fields. This is the value GPS satellites will generate and deep down it’s the one value you can be sure of. Your local time is usually an offset from UTC.

If your country or region has DWT, then there are a couple of times a year when the local time in a field can be undefined. UTC time does not have this problem. If you divide the Earth up into 24 segments, one for each hour, then you would expect 24 different time zones to be in place. But there are more than that.

Most places use a multiple of hours plus or minus UTC, so you would think plus or minus 12 hours would be enough. But there are half-hour increments of time zones.

We saw a report once designed with a parameter with a UTC offset, expecting an integer value for the hours offset. Well, some places have a half hour offset including Adelaide, Darwin, Rangoon, and New Delhi. Then there is the strange situation of the Chatham Islands which is 12:45 ahead of UTC and one wonders what time they use at the base at the South Pole in Antarctica which can be in any time zone with a small step. Or the North Pole, for that matter.

Further adding to the confusion, some countries span multiple time zones in an effort to stay close to the 24 segment approach while others ignore it entirely. China has one time zone covering the entire country.