/**
 * Split a time interval into sub-intervals of `amount × unit`.
 *
 * - Returns an array of `{ start, end }` records that tile the interval.
 * - The final sub-interval is trimmed so its `end` never exceeds the original `end`.
 * - Returns `[{ start, end }]` when `start === end` (zero-length interval).
 * - Returns `[]` on invalid input (unparseable start/end, unsupported unit, non-positive amount,
 *   or a unit that has no effect on `PlainTime`, e.g. `"days"`).
 *
 * @param start ISO PlainTime string for the interval start
 * @param end ISO PlainTime string for the interval end
 * @param unit duration unit string — `"hours" | "minutes" | "seconds" | "milliseconds" | "microseconds" | "nanoseconds"` (calendar units are ignored by PlainTime and return [])
 * @param amount positive number of units per step
 * @returns array of `{ start, end }` records, or [] on invalid input
 *
 * @example splitIntervalByUnitTime("12:00:00", "14:00:00", "hour", 1) // [{ start: "12:00:00", end: "13:00:00" }, { start: "13:00:00", end: "14:00:00" }]
 * @example splitIntervalByUnitTime("12:00:00", "14:30:00", "hour", 1) // [{ start: "12:00:00", end: "13:00:00" }, { start: "13:00:00", end: "14:00:00" }, { start: "14:00:00", end: "14:30:00" }]
 * @example splitIntervalByUnitTime("12:00:00", "12:00:00", "hour", 1) // [{ start: "12:00:00", end: "12:00:00" }]
 * @example splitIntervalByUnitTime("12:00:00", "14:00:00", "hour", 0) // []
 * @example splitIntervalByUnitTime("invalid", "14:00:00", "hour", 1) // []
 */
export declare function splitIntervalByUnitTime(start: string, end: string, unit: string, amount: number): Array<{
    start: string;
    end: string;
}>;