We compare the performance of two JavaScript implementations for detecting time changes, such as Daylight Saving Time (DST), across various time zones and date ranges. The primary implementation leverages Intl.DateTimeFormat, a modern and efficient API that reuses its formatter, significantly reducing the time (0 ms) required to compute results. In contrast, the proposed polyfill relies on Date.toLocaleTimeString, which, while offering broader compatibility, is notably slower (0 ms) as it does not benefit from formatter reuse.
| Timezone | Records | With Intl (ms) | Without Intl (ms) | Same Output | Jump found |
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The polyfill serves as an alternative for environments where Intl.DateTimeFormat might not be available, ensuring the TimeZoneShift function can still operate effectively. The Intl.DateTimeFormat method is substantially faster than the polyfill, particularly when dealing with large sets of data. This is due to its ability to efficiently reuse formatters, making it the preferred choice for performance-critical applications, even when a single record is needed.
JavaScript engines like V8 (used in Chrome) and SpiderMonkey (used in Firefox) rely on the host operating system's (Windows) time zone data, which may introduce discrepancies between different environments or versions.