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@burglekitt/gmt

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Temporal-based date and time utilities with timezone support and polyfill integration

github.com/burglekitt/gmt

burglekitt/gmt

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/** * Return the locale-relative day-of-week index for `value`. * * - `0` = the locale's first day of week (e.g. Sunday for en-US, Monday for fr-FR). * - Resolves the locale's first day of week via `Intl.Locale.prototype.weekInfo`. * - Falls back to Monday if the runtime's `weekInfo` data doesn't resolve * a first day for the locale. * - Returns `null` if `value` is not a valid ISO date or `locale` is unresolvable. * * @param value ISO 8601 date string * @param locale BCP 47 locale tag (e.g. "en-US", "fr-FR") * @returns locale-relative day-of-week index (0–6) or null on invalid input * * @example getLocaleDayOfWeek("2024-02-25", "en-US") // 0 (Sunday) * @example getLocaleDayOfWeek("2024-02-26", "en-US") // 1 (Monday) * @example getLocaleDayOfWeek("2024-02-26", "fr-FR") // 0 (Monday) * @example getLocaleDayOfWeek("invalid-date", "en-US") // null * @example getLocaleDayOfWeek("2024-02-29", "not-a-locale") // null */ export declare function getLocaleDayOfWeek(value: string, locale: string): number | null;