Convert string to timestamp for Spark using Scala

Well, if you want to cast the date_timecolumn to timestampand create a new column with the year value then do exactly that:

import org.apache.spark.sql.functions.year

df
  .withColumn("date_time", $"date_time".cast("timestamp"))  // cast to timestamp
  .withColumn("year", year($"date_time"))  // add year column