/**
 * Locale-aware date formatting built on the native `Intl.DateTimeFormat`.
 * No locale tables are bundled — output follows the runtime's ICU data for the
 * given BCP 47 locale tag.
 */
/**
 * Get localized weekday names.
 *
 * @param locale - BCP 47 locale tag (e.g. 'de-DE')
 * @param weekStartsOn - Day the week starts on (0=Sun, 1=Mon)
 * @param format - Name format ('narrow'='M', 'short'='Mo', 'long'='Montag')
 * @returns Array of 7 weekday name strings, ordered from `weekStartsOn`
 */
export declare function getWeekdayNames(locale?: string, weekStartsOn?: number, format?: 'narrow' | 'short' | 'long'): string[];
/** Format month and year for header display, e.g. "März 2026", "March 2026". */
export declare function formatMonthYear(year: number, month: number, locale?: string): string;
/** Format a date for a detail header, e.g. "Do, 12. März", "Thu, March 12". */
export declare function formatDate(date: Date, locale?: string, options?: Intl.DateTimeFormatOptions): string;
/** Format a date for a screen-reader label, e.g. "Donnerstag, 12. März 2026". */
export declare function formatDateFull(date: Date, locale?: string): string;
/**
 * Format a week title for a header, e.g. "KW 12 – März 2026" (de-DE) or
 * "Week 12 – March 2026" (en-US). Uses the week's Thursday to pick the
 * month/year (ISO week convention).
 */
export declare function formatWeekTitle(date: Date, weekStartsOn?: number, locale?: string): string;
/**
 * Format the date span of the week containing `date`, e.g. "15.–21. Juni"
 * (de-DE) or "Jun 15 – 21" (en-US). The exact shape — and whether the shared
 * month collapses — follows the locale via `Intl.DateTimeFormat.formatRange`.
 */
export declare function formatWeekRange(date: Date, locale?: string, weekStartsOn?: number): string;
/**
 * Format an arbitrary date span including the year, e.g. "15. Juni – 5. Juli
 * 2026" (de-DE). Collapses shared month/year parts per the locale via
 * `Intl.DateTimeFormat.formatRange`. Suited to a multi-week range-view title;
 * for a single ISO week prefer {@link formatWeekRange}.
 */
export declare function formatDateRange(start: Date, end: Date, locale?: string): string;
/**
 * Format a day-view header, e.g. "Do, 19. März 2026" (de-DE) or
 * "Thu, March 19, 2026" (en-US).
 */
export declare function formatDayTitle(date: Date, locale?: string): string;
/**
 * Format the clock time of an appointment, e.g. "9:05" / "09:05–10:30 Uhr"
 * (de-DE), "9:05 AM" / "9:05 – 10:30 AM" (en-US).
 *
 * The shape is the locale's own, not a hardcoded 24-hour string: the hour cycle,
 * the separator, the zero-padding and any suffix all come from ICU via
 * `Intl.DateTimeFormat`. That is also why the two arms of one locale can look
 * different — German pads the hour and appends "Uhr" in the *range* pattern
 * only. Treat the samples above as illustrations, not as a contract: the exact
 * punctuation follows the runtime's ICU data and shifts between versions (Bun
 * and Node already disagree on the "Uhr").
 *
 * `end` is rendered **only when it falls on the same calendar day as `start`**.
 * `formatRange` otherwise widens to the full date on both sides
 * ("15.6.2026, 09:00 – 17.6.2026, 17:00"), which is a paragraph in a list row.
 * A caller listing a span across days therefore states one end per row and says
 * so — `CalendarEventItem` passes `start` on the event's first day and calls
 * this again with the bare `end` (no second argument) on its last. The guard
 * doubles as the invalid-`end` net: an unparseable date is never "the same
 * day", so it drops out instead of making `formatRange` throw inside a
 * `$derived`.
 *
 * @param start - Start of the appointment (local time)
 * @param end - Optional end; ignored when it is on another day
 * @param locale - BCP 47 locale tag
 */
export declare function formatTimeRange(start: Date, end?: Date, locale?: string): string;
/**
 * Format an abbreviated month name for the year grid, e.g. "Mär" (de-DE) or
 * "Mar" (en-US).
 *
 * @param month - Month index (0-11)
 * @param locale - BCP 47 locale tag
 */
export declare function formatMonthShort(month: number, locale?: string): string;