/**
 * Checks if the given value is a valid Date object.
 *
 * @param value - The value to check.
 * @returns True if the value is a Date object and represents a valid date, false otherwise.
 *
 * @example
 * ```typescript
 * isDate(new Date()); // true
 * isDate("2025-03-12"); // false
 * isDate(new Date("invalid date")); // false
 * ```
 */
export declare function isDate(value: unknown): value is Date;