import { Temporal } from "@js-temporal/polyfill";
import type { FractionalDigit } from "../../types/index.js";
/**
 * Compare two ISO datetime strings for equality at a given unit.
 *
 * - Equality means both values share the same start-of-`unit` boundary, so
 *   `"month"` requires the same month AND year — March 2023 and March 2024 are
 *   NOT equal by month, matching date-fns's `isSameMonth` and Luxon's
 *   `dt.hasSame(other, "month")`.
 * - Supports the full `Temporal.DateUnit | Temporal.TimeUnit` range, down to
 *   `"nanosecond"`.
 * - Returns false for an unsupported unit or invalid input.
 *
 * Mapping from date-fns (Decision 5, `context/roadmap/issues/J.md`):
 * - `isSameDay(a, b)` → `areDateTimesEqualBy(a, b, "day")`
 * - `isSameHour(a, b)` → `areDateTimesEqualBy(a, b, "hour")`
 * - `isSameMinute(a, b)` → `areDateTimesEqualBy(a, b, "minute")`
 * - `isSameSecond(a, b)` → `areDateTimesEqualBy(a, b, "second")`
 * - `isSameMonth(a, b)` → `areDateTimesEqualBy(a, b, "month")`
 * - `isSameYear(a, b)` → `areDateTimesEqualBy(a, b, "year")`
 *
 * @param value1 first ISO datetime string
 * @param value2 second ISO datetime string
 * @param unit Temporal.DateUnit | Temporal.TimeUnit to compare by
 * @param optionsArg optional: weekStartsOn ("monday" | "sunday"), fractionalSecondDigits (number)
 * @returns true if both datetimes share the same start-of-unit boundary, false on an unsupported unit or invalid input
 *
 * @example areDateTimesEqualBy("2024-03-15T10:00:00", "2024-03-15T18:00:00", "day") // true
 * @example areDateTimesEqualBy("2024-03-15T10:30:00", "2024-03-15T10:45:00", "hour") // true
 * @example areDateTimesEqualBy("2024-03-15T10:30:00", "2024-03-15T11:00:00", "hour") // false
 * @example areDateTimesEqualBy("2023-03-15T10:00:00", "2024-03-15T10:00:00", "month") // false (same month, different year)
 * @example areDateTimesEqualBy("invalid", "2024-03-15T10:00:00", "day") // false
 */
export declare function areDateTimesEqualBy(value1: string, value2: string, unit: Temporal.DateUnit | Temporal.TimeUnit, optionsArg?: {
    weekStartsOn?: "monday" | "sunday";
    fractionalSecondDigits?: FractionalDigit;
}): boolean;