Hi Peenuts, In Impala we try to have the following policy when converting timestamps to different timezones: In case of ambiguity, return NULL. Ambiguity means that we could return more than one answer. When daylight savings time switch happens in the fall, the same hour happens twice (between 1-2 am), so if we see "1:30 am", we can't tell if that point in time is before the swtich, or after. Interestingly, when the daylight savings switch happens in the spring, the hour between 2am and 3am does not exist at all.
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