When LEGACY, java.text.SimpleDateFormat is used for formatting and parsing dates/timestamps in a locale-sensitive manner, which is the approach before Spark 3.0. 

When set to CORRECTED, classes from java.time.* packages are used for the same purpose. The default value is EXCEPTION, RuntimeException is thrown when we will get different results.

spark.conf.set("spark.sql.legacy.timeParserPolicy","LEGACY") 

or

spark.sql("set spark.sql.legacy.timeParserPolicy=LEGACY")