Github user zivanfi commented on a diff in the pull request:
https://github.com/apache/spark/pull/19250#discussion_r143257840
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/datetimeExpressions.scala
---
@@ -1213,6 +1213,71 @@ case class ToUTCTimestamp(left: Expression, right:
Expression)
}
/**
+ * This modifies a timestamp to show how the display time changes going
from one timezone to
+ * another, for the same instant in time.
+ *
+ * We intentionally do not provide an ExpressionDescription as this is not
meant to be exposed to
+ * users, its only used for internal conversions.
+ */
+private[spark] case class TimestampTimezoneCorrection(
--- End diff --
Unfortunately the offset depends on the actual date, so a timezone
conversion can not be simplified to a simple delta.
Daylight saving time starts and ends on different days in different
timezones, while some timezones don't have DST changes at all. Additionally,
timezone rules have changed over time and keep changing. Both the basic
timezone offset and the DST rules themselves could change (and have changed)
over time.
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