/**
 * Date utilities for bridging form values, ISO strings, and `Date` objects.
 *
 * Components like {@link DatePicker} accept either a `Date` or an ISO
 * timestamp on input. When the surrounding state holds ISO strings (for
 * example because the database driver serialises timestamps that way),
 * use these helpers to convert in both directions instead of redoing the
 * arithmetic at every form site.
 *
 * The strict `YYYY-MM-DD` ↔ `Date` core is not reimplemented here: it lives in
 * `../date/range` (`toIso` / `isoToDate`, the Layer-0 source of truth). These
 * tolerant form helpers delegate to it and only add the tolerant shape rules
 * (empty/undefined → nullish, 1-digit month/day, epoch-number coercion).
 */
/** Shared union for utilities that accept any common "date-ish" input. */
export type DateInput = Date | string | number | null | undefined;
/** Month index used by `Date#getMonth()`. */
export type MonthIndex = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11;
/** Weekday index used by `Date#getDay()`. */
export type WeekdayIndex = 0 | 1 | 2 | 3 | 4 | 5 | 6;
/**
 * Coerce a `Date`, ISO timestamp, epoch-ms number, or empty value into a
 * `Date`. Returns `undefined` for empty / unparseable inputs.
 *
 * Shape rules:
 * - Strings of the form `YYYY-MM-DD` are parsed in LOCAL timezone
 *   (matching `<input type="date">` and `toDateInputValue` round-trip).
 * - Numbers smaller than ~100 s past epoch are rejected as ambiguous
 *   (programmer error — `2026` passed instead of a real timestamp).
 *   Legitimate pre-2001 epoch ms (e.g. birthdays) are accepted.
 * - Invalid `Date` instances and unparseable strings log a warning
 *   instead of disappearing silently.
 */
export declare function coerceToDate(input: DateInput): Date | undefined;
/**
 * Format a date as the `YYYY-MM-DD` string accepted by
 * `<input type="date">` and the DatePicker text rendering. Returns
 * an empty string for null / invalid inputs so it can be assigned
 * directly to a form field's `value`.
 */
export declare function toDateInputValue(d: Date | string | null | undefined): string;
/**
 * Parse a `YYYY-MM-DD` (or any other `Date`-parseable) string into a
 * `Date`. `YYYY-MM-DD` is interpreted as LOCAL midnight to round-trip
 * with `toDateInputValue`; full ISO timestamps with timezone are passed
 * to the native parser unchanged. Returns `null` for empty or malformed
 * input so the caller decides how to surface the error.
 */
export declare function fromDateInputValue(s: string | null | undefined): Date | null;