code: function init() {
      var options = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};
  
      dayStartsAt = options.dayStartsAt || DEFAULT_DAY_STARTS_AT;
      nightStartsAt = options.nightStartsAt || DEFAULT_NIGHT_STARTS_AT;
    }
docs: Initialize with defaults
  @param {Object} [options]
  - {Number} dayStartsAt
  - {Number} nightStartsAt
  - {Array} parseKeys