/**
 * Built-in date/time functions: TODAY, NOW, YEAR, MONTH, DAY.
 *
 * Dates use the **Excel serial-number model**: day 1 is 1900-01-01, so a date is
 * a number of days since the 1899-12-30 epoch and a datetime carries a
 * fractional day. TODAY/NOW read the injected {@link EvalContext.now} clock (not
 * `Date.now()`), keeping them deterministic under test and stable within a
 * single recalculation pass. All arithmetic is done in UTC for determinism.
 *
 * @packageDocumentation
 */
import type { FormulaFunction } from './formula-function';
import { FunctionCategory } from './formula-function';
import type { EvalContext } from '../types/eval-context';
import type { FormulaArgument, FormulaValue } from '../types/formula.types';
/** `TODAY()` — today's date as an Excel serial number (integer). Volatile. */
export declare class TodayFunction implements FormulaFunction {
    readonly name = "TODAY";
    readonly category = FunctionCategory.DateTime;
    readonly minArgs = 0;
    readonly maxArgs = 0;
    readonly volatile = true;
    readonly description = "Returns today's date as a serial number.";
    evaluate(_args: readonly FormulaArgument[], ctx: EvalContext): FormulaValue;
}
/** `NOW()` — current date and time as an Excel serial number. Volatile. */
export declare class NowFunction implements FormulaFunction {
    readonly name = "NOW";
    readonly category = FunctionCategory.DateTime;
    readonly minArgs = 0;
    readonly maxArgs = 0;
    readonly volatile = true;
    readonly description = "Returns the current date and time as a serial number.";
    evaluate(_args: readonly FormulaArgument[], ctx: EvalContext): FormulaValue;
}
/** Base for the YEAR/MONTH/DAY extractors. */
declare abstract class DatePartFunction implements FormulaFunction {
    abstract readonly name: string;
    readonly category = FunctionCategory.DateTime;
    readonly minArgs = 1;
    readonly maxArgs = 1;
    evaluate(args: readonly FormulaArgument[]): FormulaValue;
    /** Extracts the desired UTC calendar part from `d`. */
    protected abstract part(d: Date): number;
}
/** `YEAR(date)` — the 4-digit year. */
export declare class YearFunction extends DatePartFunction {
    readonly name = "YEAR";
    readonly description = "Returns the year of a date.";
    protected part(d: Date): number;
}
/** `MONTH(date)` — the month (1–12). */
export declare class MonthFunction extends DatePartFunction {
    readonly name = "MONTH";
    readonly description = "Returns the month of a date (1\u201312).";
    protected part(d: Date): number;
}
/** `DAY(date)` — the day of the month (1–31). */
export declare class DayFunction extends DatePartFunction {
    readonly name = "DAY";
    readonly description = "Returns the day of the month of a date (1\u201331).";
    protected part(d: Date): number;
}
export {};
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