- Calculations and comparisons of DateTime instances are only meaningful when the instances being compared or used are representations of points in time from the same time-zone perspective.
- A developer is responsible for keeping track of time-zone information associated with a DateTime value via some external mechanism. Typically this is accomplished by defining another field or variable that you use to record time-zone information when you store a DateTime value type. This approach (storing the time-zone sense alongside the DateTime value) is the most accurate and allows different developers at different points in a program’s lifecycle to always have a clear understanding of the meaning of a DateTime value. Another common approach is to make it a “rule” in your design that all time values are stored in a specific time-zone context. This approach does not require additional storage to save a user’s view of the time-zone context, but introduces the risk that a time value will be misinterpreted or stored incorrectly down the road by a developer that isn’t aware of the rule.
Continue reading “DateTime – It’s all about the rules!”