Function toAbsolute

packages/@internationalized/date/src/conversion.ts:151–213

(
  date: CalendarDate | CalendarDateTime,
  timeZone: string,
  disambiguation: Disambiguation = 'compatible'
)

}

export function toAbsolute(
  date: CalendarDate | CalendarDateTime,
  timeZone: string,
  disambiguation: Disambiguation = 'compatible'
): number {
  let dateTime = toCalendarDateTime(date);

  // Fast path: if the time zone is UTC, use native Date.
  if (timeZone === 'UTC') {
    return epochFromDate(dateTime);
  }

  // Fast path: if the time zone is the local timezone and disambiguation is compatible, use native Date.
  // Skip this fast path if the local timezone was explicitly overridden via setLocalTimeZone,
  // since native Date always uses the browser's timezone, not the overridden one.
  if (
    timeZone === getLocalTimeZone() &&
    disambiguation === 'compatible' &&
    !isLocalTimeZoneOverridden()
  ) {
    dateTime = toCalendar(dateTime, new GregorianCalendar());

    // Don't use Date constructor here because two-digit years are interpreted in the 20th century.
    let date = new Date();
    let year = getExtendedYear(dateTime.era, dateTime.year);
    date.setFullYear(year, dateTime.month - 1, dateTime.day);
    date.setHours(dateTime.hour, dateTime.minute, dateTime.second, dateTime.millisecond);
    return date.getTime();
  }

  let ms = epochFromDate(dateTime);
  let offsetBefore = getTimeZoneOffset(ms - DAYMILLIS, timeZone);
  let offsetAfter = getTimeZoneOffset(ms + DAYMILLIS, timeZone);
  let valid = getValidWallTimes(dateTime, timeZone, ms - offsetBefore, ms - offsetAfter);

  if (valid.length === 1) {
    return valid[0];
  }

  if (valid.length > 1) {
    switch (disambiguation) {
      // 'compatible' means 'earlier' for "fall back" transitions
      case 'compatible':
      case 'earlier':
        return valid[0];
      case 'later':
        return valid[valid.length - 1];
      case 'reject':
        throw new RangeError('Multiple possible absolute times found');
    }
  }

  switch (disambiguation) {
    case 'earlier':
      return Math.min(ms - offsetBefore, ms - offsetAfter);
    // 'compatible' means 'later' for "spring forward" transitions
    case 'compatible':
    case 'later':