/**
 * date-core - framework-free date math shared by SvCalendar, SvTimePicker and
 * SvDateTimePicker. No Svelte, no DOM: pure functions over the native `Date`
 * so it is trivially unit- and mutation-testable and reusable standalone.
 *
 * Conventions:
 * - A "day" is compared by local calendar date (year/month/date), ignoring the
 *   time-of-day, unless a helper says otherwise.
 * - `firstDayOfWeek` is 0-6 (0 = Sunday), matching `Date.getDay()` and Smart's
 *   `firstDayOfWeek`.
 */
export type DateLike = Date | number | string;
/** Coerce a Date | epoch-ms | parseable string to a Date, or null if invalid. */
export declare function toDate(value: DateLike | null | undefined): Date | null;
/** A new Date at local midnight of the same calendar day (time stripped). */
export declare function startOfDay(d: Date): Date;
/** First day (midnight) of the month `d` falls in. */
export declare function startOfMonth(d: Date): Date;
/** Last day (midnight) of the month `d` falls in. */
export declare function endOfMonth(d: Date): Date;
/** Number of days in the month `d` falls in. */
export declare function daysInMonth(d: Date): number;
/**
 * Start of the week containing `d`, honoring `firstDayOfWeek` (0-6). Returns a
 * local-midnight Date on or before `d`.
 */
export declare function startOfWeek(d: Date, firstDayOfWeek?: number): Date;
/** True when both dates are the same local calendar day. */
export declare function isSameDay(a: Date | null, b: Date | null): boolean;
/** True when both dates are in the same year+month. */
export declare function isSameMonth(a: Date | null, b: Date | null): boolean;
/** -1 / 0 / 1 comparison by calendar day (time-of-day ignored). */
export declare function compareDay(a: Date, b: Date): number;
/** Add `n` days (can be negative), returning a new Date. */
export declare function addDays(d: Date, n: number): Date;
/**
 * Add `n` calendar months, clamping the day-of-month so 31 Jan + 1 month = 28/29
 * Feb rather than spilling into March (matches how calendars paginate).
 */
export declare function addMonths(d: Date, n: number): Date;
/** Add `n` years, clamping Feb-29 to Feb-28 on non-leap targets. */
export declare function addYears(d: Date, n: number): Date;
/** Clamp `d` to the inclusive [min, max] range (either bound may be null). */
export declare function clampDate(d: Date, min: Date | null, max: Date | null): Date;
/**
 * ISO 8601 week number (1-53) for `d`. Week 1 is the week containing the first
 * Thursday of the year; weeks start Monday. Independent of `firstDayOfWeek`,
 * matching Smart's `weekNumbers` column which is always ISO.
 */
export declare function isoWeek(d: Date): number;
/**
 * The [start, end] years of the decade block that `year` belongs to, as Smart
 * renders it: a 12-cell page running from the decade start minus 1 to plus 10
 * (one leading + one trailing year for context). We expose the canonical
 * decade [Y0, Y0+9] and let the view pad.
 */
export declare function decadeRange(year: number): {
    start: number;
    end: number;
};
/** The [start, end] years of the century block (100-year) `year` belongs to. */
export declare function centuryRange(year: number): {
    start: number;
    end: number;
};
export type MonthMatrixCell = {
    date: Date;
    /** In the displayed month (vs. leading/trailing days of adjacent months). */
    inMonth: boolean;
    /** ISO week number of the row this cell sits in. */
    week: number;
};
/**
 * Build a month grid of `weeks` rows x 7 columns starting at `firstDayOfWeek`,
 * padded with the trailing days of the previous month and leading days of the
 * next so every row is full. `weeks` defaults to 6 (the max any month needs),
 * matching Smart's fixed-height calendar.
 */
export declare function monthMatrix(monthDate: Date, firstDayOfWeek?: number, weeks?: number): MonthMatrixCell[][];
/**
 * Ordered weekday indexes (0-6) for a header row starting at `firstDayOfWeek`.
 * e.g. firstDayOfWeek=1 -> [1,2,3,4,5,6,0].
 */
export declare function weekdayOrder(firstDayOfWeek?: number): number[];
/** Merge a calendar day with a time-of-day taken from `time`, returning a new Date. */
export declare function withTime(day: Date, time: Date): Date;
/** Snap a minute value to the nearest lower multiple of `interval` (>=1). */
export declare function snapMinute(minute: number, interval: number): number;