/**
 * Collapse a list of date intervals into the minimum set of non-overlapping intervals.
 *
 * - List-form generalization of `intervalUnionDate`, which is pairwise only.
 * - Intervals are merged when they overlap or share an endpoint exactly (adjacent intervals,
 *   e.g. `aEnd === bStart`, ARE merged — same rule as `intervalUnionDate`).
 * - Order of the input list does not matter; the result is sorted by start.
 * - Returns `[]` for an empty list.
 * - Returns `[]` when `intervals` is not an array, when any element is not a
 *   `{ start, end }` record of valid ISO PlainDate strings, or when any element has
 *   `start > end`.
 * - Accepts GMT calendar-annotated PlainDate strings — E5 (issue #78). Since the result is
 *   date *values*, every `start`/`end` across the whole list must carry the *same* calendar tag
 *   (or all be bare ISO); any mismatch returns `[]` (E5 decision of record D4).
 *
 * @param intervals array of `{ start, end }` records, optionally calendar-annotated
 * @returns the minimum set of non-overlapping `{ start, end }` records, sorted by start, or `[]` on invalid input / mismatched calendars
 *
 * @example mergeIntervalsDate([{ start: "2024-01-01", end: "2024-01-10" }, { start: "2024-01-05", end: "2024-01-15" }]) // [{ start: "2024-01-01", end: "2024-01-15" }]
 * @example mergeIntervalsDate([{ start: "2024-01-01", end: "2024-01-10" }, { start: "2024-01-10", end: "2024-01-20" }]) // [{ start: "2024-01-01", end: "2024-01-20" }] (adjacent, merged)
 * @example mergeIntervalsDate([{ start: "2024-01-01", end: "2024-01-05" }, { start: "2024-01-10", end: "2024-01-15" }]) // [{ start: "2024-01-01", end: "2024-01-05" }, { start: "2024-01-10", end: "2024-01-15" }] (disjoint)
 * @example mergeIntervalsDate([]) // []
 * @example mergeIntervalsDate([{ start: "2024-01-10", end: "2024-01-01" }]) // []
 */
export declare function mergeIntervalsDate(intervals: Array<{
    start: string;
    end: string;
}>): Array<{
    start: string;
    end: string;
}>;