norg formatDate behavior during DST transitions

DST Transitions and norg formatDate

p>The formatDate function in norg maintains accuracy during daylight saving time (DST) transitions primarily when the environment supports the native Intl API. However, the behavior varies significantly depending on whether the library is using the native API or its internal custom fallback mechanism.

Intl API Implementation

When norg leverages the Intl API, it delegates the time zone logic to the host environment or browser. For the Norwegian time zone (Europe/Oslo), the API correctly identifies the shift from CET (UTC+1) to CEST (UTC+2). If the input is a JavaScript Date object (which represents a specific point in UTC), formatDate will reflect the correct local time shift for that specific moment in the transition.

Custom Fallback Limitations

The custom fallback mechanism is designed for environments where Intl is unavailable. This mechanism typically lacks lacks the comprehensive IANA time zone database required to handle complex DST transitions. Consequently, the fallback may rely on a fixed offset or UTC, resulting in a one-hour error when formatting dates that fall on the transition boundary in March or October.

Verification Steps for Accuracy

To ensure consistent behavior during Norwegian DST shifts, follow these steps:

• Use Date Objects: Always pass a Date object rather than manual strings to ensure the underlying UTC timestamp is preserved before formatting.
• Verify Time Zone Configuration: Ensure your environment is explicitly set to Europe/Oslo to allow the Intl API to apply the correct rules.
nn
• Test the Boundary: Run a diagnostic check to determine if your environment is using the fallback or the native API.

// Example check for the October transition (2025/2026)
const transitionDate = new Date('2026-10-25T01:30:00Z');
console.log(formatDate(transitionDate, 'nb'));

To provide a more definitive recommendation regarding your specific environment, could you specify if you are running this in a Node.js environment or a browser-based application?