export type UtcUnit = "year" | "month" | "week" | "day" | "dayOfWeek" | "hour" | "minute" | "second" | "millisecond";
/**
 * Extract a unit from a UTC datetime string.
 *
 * - Valid units: "year", "month", "week", "day", "dayOfWeek", "hour", "minute", "second", "millisecond".
 * - Uses Temporal.Instant.from to parse, converts to UTC.
 * - Returns "" for invalid input.
 *
 * @param value ISO UTC datetime string (e.g., "2024-03-17T14:30:45Z")
 * @param unit unit to extract from the datetime
 * @param optionsArg optional: weekStartsOn ("monday" | "sunday") for week calculations
 * @returns string representation of the requested unit or "" on invalid input
 *
 * @example parseUnitFromUtc("2024-03-17T14:30:45Z", "month") // "03"
 * @example parseUnitFromUtc("2024-01-01T00:00:00Z", "week") // "1"
 * @example parseUnitFromUtc("2024-01-01T00:00:00Z", "week", { weekStartsOn: "sunday" }) // "1"
 * @example parseUnitFromUtc("invalid", "month") // ""
 */
export declare function parseUnitFromUtc(value: string, unit: UtcUnit, optionsArg?: {
    weekStartsOn?: "monday" | "sunday";
}): string;