code: public static String stringifyValue(Param param, ObjectMapper mapper) {
  		assert !(param instanceof BinaryParam);
  		
  		if (param.value instanceof String)
  			return (String)param.value;
  		if (param.value instanceof Date)
  			return Long.toString(((Date)param.value).getTime() / 1000);
  		else if (param.value instanceof Number)
  			return param.value.toString();
  		else
  			return JSONUtils.toJSON(param.value, mapper);
  	}
docs: Stringify the parameter value in an appropriate way. Note that Facebook fucks up dates by using unix time-since-epoch
  some places and ISO-8601 others. However, maybe unix times always work as parameters?