code: function dateRelative(d, dRelative, arg1, arg2) {
    var adu, format, type, localeCode, fn;
    assertDateIsValid(d);
    if (isFunction(arg1)) {
      fn = arg1;
    } else {
      localeCode = arg1;
      fn = arg2;
    }
    adu = getAdjustedUnitForDate(d, dRelative);
    if (fn) {
      format = fn.apply(d, adu.concat(localeManager.get(localeCode)));
      if (format) {
        return dateFormat(d, format, localeCode);
      }
    }
    // Adjust up if time is in ms, as this doesn't
    // look very good for a standard relative date.
    if (adu[1] === 0) {
      adu[1] = 1;
      adu[0] = 1;
    }
    if (dRelative) {
      type = 'duration';
    } else if (adu[2] > 0) {
      type = 'future';
    } else {
      type = 'past';
    }
    return localeManager.get(localeCode).getRelativeFormat(adu, type);
  }
docs: Relative helpers