Friday, March 6, 2009

Time to “Spring Forward”

Its the most wonderful time of the year, Daylight Saving Time (DST) that is. Ah yes, those warm bright spring evenings where all the kids complain that it is too early to go to bed because “its still light out”. Perhaps that is only my house since it is light here until 10PM during the summer. The benefits of living against the edge of a time zone.

DST changed in 2007 from beginning the second Sunday of April to beginning the second Sunday in March. It ends on the first Sunday of November instead of the last Sunday in October. Although the change officially occurs at 2AM, in your local time zone, I recommend setting your clock before you go to sleep.

DST was originally proposed by Benjamin Franklin, which I learned by watching National Treasure, when he observed that people were burning candles at night but not waking up when the sun rose. It was introduced during World War I in an effort to conserve fuel used for electric power. Germany and Austria first established daylight saving time on April 30th 1916. The United States first adopted daylight saving time in March 1918.

The reasons for DST are varied ranging from better use of daylight, energy savings and safety. Although the energy savings generated by the time change are a matter of debate there are some other benefits. People are safer drivers during daylight hours and research has shown that accidents are reduced during DST.

There is a downside however. Some people have a difficult time adjusting to the time change and the impendence of heart attacks increase during the first week of DST. When “falling back” pedestrian fatalities from cars increases especially around the 6 o’clock hour. On a brighter note there is a noticeable decrease in heart attacks the week after the change back to standard time.

So what does all this trivia have to do with computers and more specifically Advantage? It has to do with the way that Windows keeps track of time. Windows stores all timestamps in Greenwich Mean Time (GMT) and adjusts based on the time zone you select. During daylight saving time an additional hour is added to the offset so all of the file times are displayed as 1 hour later. See this Microsoft article.

This is simply a cosmetic effect as the timestamp itself is not changed. However, it can still cause some confusion. To help identify the version of Advantage files we time stamp the files with our version number. For instance version 9.0 of Advantage has a time of 9:00 AM, the date varies depending on which service release you have installed. When your computer adjusts for DST the time displays as 10:00 AM.

When I worked in Advantage Tech Support I used the file time as a quick way to verify that all of the files in the server directory were the same version. Keeping in mind that these times may be displaying differently if the user is automatically adjusting for DST. If they set their computer’s clock back manually then the time would not be changed. So if the files had a time of 9:10 AM and the customer insisted they were using version 8.1 then you should ask if the machine automatically adjusts for DST.

Enjoy your weekend and remember you will get that lost hour back in November.

No comments: