GroupWise and Daylight Saving Time
Novell Cool Solutions: Feature
By Alan Smithee
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Posted: 16 Jun 1999
Novell GroupWise has always been carefully designed to recognize a basic principle of electronic communication: time is relative to the location where that communication may occur. Although the time of day varies throughout the world at any given moment, a responsible network messaging system will reconcile those differences in message time stamps and scheduled appointments. The more widespread the communication, the greater the responsibility of the messaging technology to keep the communication synchronized and useful to those who must deal with time differences.
With this premise in mind, GroupWise engineers designed GroupWise to account for and synchronize messages not only by using the finite standards of the defined world time zones, but also by using the more unevenly applied standard known as Daylight Saving Time (DST).
Understanding Time Zones
The earth's rotation from daylight to darkness and the need for constant communication between different locations in the world make it necessary to establish a system for measuring time based on a single standard. This standard, called Coordinated Universal Time (UTC) is a measurement of mean solar time beginning at a defined longitude on the earth (0·-- the prime meridian). From this longitude, traveling both east and west, timekeepers divide the earth into 24 increments of 15· longitude each. Each of these increments represents a different "standard" time zone and is numbered relative to the prime meridian by adding or subtracting one hour. Thus each time zone is referred to by its "offset" from UTC, so the world time zones are designated from -12 through 0 (UTC) to +12. UTC time designations can also be referred to as Greenwich Mean Time (GMT), so named because authorities at the Greenwich observatory in England established it as the location of the prime meridian.
Understanding Daylight Saving Time
Daylight Saving Time (DST) is the system of setting clocks one or two hours ahead of standard time so that both sunrise and sunset occur at a later hour, thus artificially moving a period of daylight to the evening hours. For example, in the northern hemisphere, clocks are usually set ahead one hour in the spring and set back to standard time in the fall. When DST is in effect in the southern hemisphere it will not be in effect in the northern hemisphere, and vice versa. Daylight Saving can be considered a political system, rather than a scientific one, because national and regional governments decide whether they will adopt the system or not. In some time zones, DST may not be used at all. Governments or institutions may define the DST starting and ending dates years in advance, but they may also change these dates at any time. For example, in 1996, most of Europe adopted a new DST standard end date setting of the last Sunday of October. Many of the countries agreeing to the change had formerly ended DST on the last Sunday of September. Because of the lack of consistent DST adoption by the world's governments, the total number of times-of-day within all time zones adds up to about 50.
Recognizing DST Issues in Versions
The constant variability in the adoption of Daylight Saving Time, the improving technology and design of GroupWise, and the need for backward compatibility have uncovered some important issues regarding GroupWise and Daylight Saving Time.
Because different versions of GroupWise deal with Daylight Saving Time configuration in different ways, and because worldwide DST is now implemented differently than it was when older versions of GroupWise were designed, you may see evidence that GroupWise is not handling time-related information correctly. Your users may report any of the following problems:
- Meetings are scheduled to start one hour earlier or later than the sender specified
- Incoming messages show an incorrect delivery time
- Status of outgoing messages shows incorrect send or receive times
These symptoms are a result of DST start and end dates being incorrectly calculated. Most commonly, this occurs because:
- The 5.x system or part of the 5.x system was migrated from GroupWise 4.1 with GroupWise 5.2 Service Pack 2 or earlier code.
- The original 4.1 system that was migrated to 5.x did not use Daylight Saving Time (that is, the DST clock change settings for the affected time zones were set at 0).
- Some of the post offices (either in 4.x or 5.x systems) used incorrect DST settings.
What to Do?
Fortunately, there is a new guide, GroupWise and Daylight Saving Time, on the web that will help you troubleshoot DST issues. In fact, the preceding sections of this page contain text shamelessly ripped off from the new guide (hereafter referred to as "the new guide"). The first section helps you decide whether you will have problems when your area switches over to Daylight Saving Time. Keep in mind that not all areas of the world use DST. In the U.S., for example, Arizona and some rebel parts of Indiana abstain from DST. If your area uses DST, you probably already know about it. We, here at Cool Solutions, are a little reluctant to make a table listing which areas around the world use DST and when; we'd leave some areas off or we'd incorrectly list the dates and make someone late for church. The second section of the new guide explains the most common GroupWise DST issues and offers possible solutions. And for your reading pleasure, the new guide contains six appendixes (or is that appendices?). So, go get the guide and get cracking. One last thing: the correct name of DST is Daylight Saving Time. Not Daylight Savings Time. Ridicule those who say it incorrectly.
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