Daylight Savings Time changes
What is DST?
Daylight Savings Time (DST) is an adjustment made to the local standard time, allowing people to make the best use of daylight during the different seasons. The mnemonic device “Spring ahead, Fall back”, refers to how one should adjust a clock to correctly navigate the move to and from DST.
New start and end dates
As an energy-saving move, the United States extended their DST by four weeks, requiring less artificially-generated hours during business hours. Most of Canada and Bermuda followed suit to keep in synch with their neighbour. Starting in 2007, DST will begin two weeks earlier, on the second Sunday in March, and will end two weeks later, on the first Sunday in November.
Impact on software
In order correctly represent the time, and to make date/time calculations, your software will need to have the DST rules internally coded. This is a well-understood issue, and your current system should seamlessly handle the adjustments required to accommodate DST. However, unless you have a very recently created system, some aspects may not refer to the new start and end dates. If this is the case, in the four new weeks of DST, the correct current time may not be represented by your system, and time span calculations for dates that cross on or more of the DST transition dates may be incorrect.
Risk assessment
Before making a change to your system, determine whether the system will be affected by the new daylight savings time dates. If it does not rely on calculating, storing and displaying date/time values, you might not need to make any change to your system, even if it does not been recently updated.
If you determine that your system will be affected, make an assessment to ensure the impact is sufficient to warrant making the change. What is the cost to your business to have incorrect time and/or date/time calculations for the period, versus the cost in bringing your system down to apply the required changes? Do you have any system upgrades already scheduled, during which you could apply updates to revise the DST rules, gaining two birds with one system outage?
Making the change
Once you’ve decided you need to make the upgrade, you will need to understand your system, to determine which portions will need to be updated. At 2Paths, we focus on J2EE web applications using Postgres databases. For such systems, the operating system, Java Runtime Environment (JRE) and database are all candidates for upgrades. The latest versions of each have the new DST rules are in place, and once these have been added, your system should handle the new Daylight Savings Time dates correctly.
