code: def datediff(end, start):
      
      sc = SparkContext._active_spark_context
      return Column(sc._jvm.functions.datediff(_to_java_column(end), _to_java_column(start)))
docs: Returns the number of days from `start` to `end`.
  
      >>> df = spark.createDataFrame([('2015-04-08','2015-05-10')], ['d1', 'd2'])
      >>> df.select(datediff(df.d2, df.d1).alias('diff')).collect()
      [Row(diff=32)]