Github user ckadner commented on the issue: https://github.com/apache/spark/pull/13652 @davies ...just to confirm the desired behavior of these two test cases ```from UTC timestamp``` and ```to UTC timestamp```. We are contending with 3 time zones: * we are parsing ```Timestamp```s from ```String```s in any/all time zones in the Java world (```DateTimeTestUtils.ALL_TIMEZONES)```) so that they represent the human readable time in any/each of those time zones which we are iterating over (*) * but in the inner ```test``` method we are treating these timestamps ```utc: String```as if they were created in ```UTC``` * then we are converting these timestamps (of "mistaken identity") to yet another time zone ```tz: String``` (i.e. ```"UTC", "JST", "PST", "Asia/Shanghai"```) and generating the human readable time in the time zone of the for-loop (```DateTimeTestUtils.withDefaultTimeZone(tz)```) ```scala test("from UTC timestamp") { def test(utc: String, tz: String, expected: String): Unit = { assert(toJavaTimestamp(fromUTCTime(fromJavaTimestamp(Timestamp.valueOf(utc)), tz)).toString === expected) } for (tz <- DateTimeTestUtils.ALL_TIMEZONES) { DateTimeTestUtils.withDefaultTimeZone(tz) { test("2011-12-25 09:00:00.123456", "UTC", "2011-12-25 09:00:00.123456") test("2011-12-25 09:00:00.123456", "JST", "2011-12-25 18:00:00.123456") test("2011-12-25 09:00:00.123456", "PST", "2011-12-25 01:00:00.123456") test("2011-12-25 09:00:00.123456", "Asia/Shanghai", "2011-12-25 17:00:00.123456") } } ... ``` (*) Before your fix (without the for-loop) the third time zone involved was determined by the user's JVM default Timezone. If this 3-timezone behavior is what we want to test, then should you replace the two occurrences of ... ```scala DateTimeTestUtils.withDefaultTimeZone(TimeZone.getTimeZone("PST")) { ``` with ... ```scala for (tz <- DateTimeTestUtils.ALL_TIMEZONES) { DateTimeTestUtils.withDefaultTimeZone(tz) { ``` ... or would ```2016-03-13 02:00:00 PST``` and ```2016-11-06 01:00:00 PST``` not work? ```scala DateTimeTestUtils.withDefaultTimeZone(TimeZone.getTimeZone("PST")) { // Daylight Saving Time test("2016-03-13 01:59:59", "PST", "2016-03-13 09:59:59.0") // 2016-03-13 02:00:00 PST does not exists test("2016-03-13 02:00:00", "PST", "2016-03-13 10:00:00.0") test("2016-03-13 03:00:00", "PST", "2016-03-13 10:00:00.0") test("2016-11-06 00:59:59", "PST", "2016-11-06 07:59:59.0") // 2016-11-06 01:00:00 PST could be 2016-11-06 08:00:00 UTC or 2016-11-06 09:00:00 UTC test("2016-11-06 01:00:00", "PST", "2016-11-06 09:00:00.0") test("2016-11-06 01:59:59", "PST", "2016-11-06 09:59:59.0") test("2016-11-06 02:00:00", "PST", "2016-11-06 10:00:00.0") } ```
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