TST: add datetimelike tests for tz-aware DatetimeIndex by azjps · Pull Request #17694 · pandas-dev/pandas (original) (raw)

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_holder here will also be DatetimeIndex, which isn't sufficient because DatetimeIndex constructor doesn't have TZ information. The problem is that the constructor DatetimeIndex(index.values, ...) is getting a numpy datetime64 array of tz-naive timestamps. There currently doesn't seem to be an argument to DatetimeIndex's constructor to tell it what timezone to convert to presuming that the input data is UTC (the tz= argument localizes to the specified timezone), so there's not currently a way to do this through init_kwargs. Hence why I currently call _fix_tz to first localize to UTC and then convert to the TZ of create_index().

To sum up:

• index = create_index() has TZ = US/Eastern
• result = index_type(index.values) has TZ = None ❌
• result = index_type(index.values, tz=index.tz) has TZ = US/Eastern, but because of re-localization has been shifted again, and thus has differently underlying values. ❌
• self._fix_tz(result, index) does have TZ = US/Eastern

I can do the suggested refactor though.