raise when date_range would return Date but time_zone was specified

[Wainberg]

raise when date_range would return Date but time_zone was specified

[MarcoGorelli]

thanks for the report

the docs say

Time zone of the resulting Datetime data type. Only takes effect if the output column is of type Datetime.

furthermore

In a future version of Polars, date_range will always return a Date.

so, this argument will just be removed from date_range eventually

For now, the suggestion

Or at a minimum, there should be an error when time zones are specified and the output would be a date.

sounds good

[mcrumiller]

In your first example, you're using date_range to construct a Datetime series, which is explicitly warned against in the docs:

Deprecated since version 0.19.3: In a future version of Polars, date_range will always return a Date. Please use datetime_range() if you want a Datetime instead.

Both of your cases look correct to me. In the first case, New York uses EST, and your output is labeled EST.

The second "incorrect" case also look correct to me. When converting from datetime to date, the time zone is completely irrelevant: Dec 31 at 23:59 is still Dec 31 regardless of what time zone you're in. You're starting on Jan 1, incrementing by 2 days at a time, up until the 3rd. So you get the 1st and the 3rd.

Edit: I see, the error is that you expect a datetime here.

[Wainberg]

@MarcoGorelli sounds good!

[stinodego]

This will all be taken care of in the scheduled deprecation. We should not make changes to deprecated functionality if not absolutely necessary.