Date helpers

// Calendar-day helpers. Everything works in local time at midnight, which is what// react-day-picker uses; ISO `YYYY-MM-DD` strings are for URLs and storage.export type DayRange = { from: Date | undefined; to?: Date | undefined };export function startOfDay(date: Date): Date {  return new Date(date.getFullYear(), date.getMonth(), date.getDate());}export function today(): Date {  return startOfDay(new Date());}export function addDays(date: Date, days: number): Date {  const next = startOfDay(date);  next.setDate(next.getDate() + days);  return next;}export function isSameDay(a: Date | undefined, b: Date | undefined): boolean {  return !!a && !!b && a.getFullYear() === b.getFullYear() && a.getMonth() === b.getMonth() && a.getDate() === b.getDate();}/** `date` moved inside [min, max] when it falls outside. */export function clampDate(date: Date, min?: Date, max?: Date): Date {  if (min && date < min) return min;  if (max && date > max) return max;  return date;}/** `2026-09-13`. */export function toIsoDate(date: Date): string {  const month = String(date.getMonth() + 1).padStart(2, "0");  const day = String(date.getDate()).padStart(2, "0");  return `${date.getFullYear()}-${month}-${day}`;}/** Parses `YYYY-MM-DD` as local midnight; anything else is undefined. */export function parseIsoDate(value: string | null | undefined): Date | undefined {  if (!value || !/^\d{4}-\d{2}-\d{2}$/.test(value)) return undefined;  const [year, month, day] = value.split("-").map(Number);  const date = new Date(year, month - 1, day);  return date.getMonth() === month - 1 ? date : undefined;}/** `Sep 13, 2026`. */export function formatDate(date: Date, locale = "en-US"): string {  return date.toLocaleDateString(locale, { month: "short", day: "numeric", year: "numeric" });}/** `Sep 7 – Sep 13, 2026`, dropping the year from the start when both ends share it. */export function formatDateRange(range: DayRange | undefined, locale = "en-US"): string | null {  const { from, to } = range ?? {};  if (!from && !to) return null;  if (from && !to) return `From ${formatDate(from, locale)}`;  if (!from && to) return `Until ${formatDate(to, locale)}`;  if (isSameDay(from, to)) return formatDate(from!, locale);  const sameYear = from!.getFullYear() === to!.getFullYear();  const start = from!.toLocaleDateString(locale, { month: "short", day: "numeric", ...(sameYear ? {} : { year: "numeric" }) });  return `${start} – ${formatDate(to!, locale)}`;}