timefilter.scala

val filterRecentTimeUDF : Long => UserDefinedFunction = {

      (l : Long) => {
        functions.udf(
        // s refers to eventTime, t refers to userEventTime
          (s : Timestamp, t: Timestamp) => if (s.getTime - t.getTime < l) true else false
        )
      }
    }

    val day : Long = 1000*60*60*24
    val week : Long = day * 7
    val month : Long = week * 4

(s.getTime - t.getTime < l) already return a boolean value. don't need to apply if else.