(function exposeCalendar(root, factory) {
  const api = factory();
  if (typeof module === "object" && module.exports) module.exports = api;
  if (root) root.ValleyCalendar = api;
})(typeof window === "undefined" ? globalThis : window, () => ({
  birthdayOn(birthdays, season, day, year) {
    const entry = birthdays?.[season]?.[day];
    if (!entry || (entry[1] && entry[1] !== year)) return null;
    return entry[0];
  }
}));