/**
 * Supported duration units for date arithmetic.
 * - ms: milliseconds
 * - s: seconds
 * - m: minutes
 * - h: hours
 * - d: days
 * - w: weeks
 * - M: months (calendar-aware)
 * - y: years (calendar-aware)
 */
export type DurationUnit = "ms" | "s" | "m" | "h" | "d" | "w" | "M" | "y";