/**
 * Pure, framework-free date formatting for content metadata. Kept fs-free so both the
 * backend content classes (`Blog`, `Docs`) and the React components can import it without
 * pulling in `node:fs`.
 */
/**
 * Normalises a raw front-matter date value to an ISO `YYYY-MM-DD` string. Front-matter is
 * parsed as YAML, whose native date type turns an *unquoted* `date: 2026-06-28` into a `Date`
 * object - only a quoted `"2026-06-28"` stays a string. This coerces either form to the
 * `YYYY-MM-DD` string the metadata contract expects, so an author who omits the quotes does not
 * silently lose the date (it feeds the rendered date, the JSON-LD `datePublished`, the
 * OpenGraph `publishedTime`, and any date sort).
 *
 * @param value - the raw front-matter value (a string, a YAML `Date`, or anything else).
 * @returns the `YYYY-MM-DD` string; a string passes through unchanged, a valid `Date` is
 *   formatted at UTC, and any other value (including an invalid `Date`) yields `undefined`.
 */
export declare function isoDateString(value: unknown): string | undefined;
/**
 * Formats an ISO `YYYY-MM-DD` date as a human-readable long date (e.g. "28 June 2026").
 *
 * The date is interpreted at UTC midnight so the rendered day never shifts with the
 * host timezone. Empty or unparseable input is returned unchanged, which lets callers
 * pass a page's raw `date` field straight through.
 *
 * @param iso - the ISO date string (`YYYY-MM-DD`); empty or invalid input is returned as-is.
 * @param locale - the BCP 47 locale used for month/day names. Defaults to `en-GB`.
 * @returns the formatted date (French: "1er" for the first of the month), or the original string
 *   when it is empty or unparseable.
 */
export declare function formatDate(iso: string, locale?: string): string;