BUG: rounding dates to 30mins does not work

[Andre-Medina]

Pandas version checks

• [X] I have checked that this issue has not already been reported.

• [X] I have confirmed this bug exists on the latest version of pandas.

• [X] I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd

dates = pd.Series([pd.to_datetime("2022-01-11 12:10:00")])

# date should be rounded but is not
dates.round("30min")
# >0   2022-01-11 12:10:00
# >dtype: datetime64[ns]

# Round just date works
dates[0].round("30min")
# >Timestamp('2022-01-11 12:00:00')

Issue Description

Issue with the latest version of pandas (2.2.0). Rounding dates at 30 min increments does not round dates if they are in a series. This was working in pandas (2.1.4)

Expected Behavior

Dates should be rounded to 30 minute increments

import pandas as pd

dates = pd.Series([pd.to_datetime("2022-01-11 12:10:00")])

# Round just date works
dates[0].round("30min")

Installed Versions

INSTALLED VERSIONS ------------------ commit : 53525ea1c333579ee612244ddea4958d900844fc python : 3.10.0.final.0 python-bits : 64 OS : Linux OS-release : 5.15.133.1-microsoft-standard-WSL2 Version : #1 SMP Thu Oct 5 21:02:42 UTC 2023 machine : x86_64 processor : byteorder : little LC_ALL : None LANG : en_US.UTF-8 LOCALE : en_US.UTF-8 pandas : 3.0.0.dev0+152.g53525ea1c3 numpy : 1.26.2 pytz : 2023.3.post1 dateutil : 2.8.2 setuptools : 68.2.2 pip : 23.3.1 Cython : None pytest : 7.4.3 hypothesis : None sphinx : None blosc : None feather : None xlsxwriter : 3.1.9 lxml.etree : None html5lib : None pymysql : None psycopg2 : None jinja2 : 3.1.2 IPython : 8.18.1 pandas_datareader : None adbc-driver-postgresql: None adbc-driver-sqlite : None bs4 : 4.12.2 bottleneck : None dataframe-api-compat : None fastparquet : None fsspec : 2023.12.2 gcsfs : 2023.12.2post1 matplotlib : 3.8.2 numba : 0.58.1 numexpr : None odfpy : None openpyxl : 3.1.2 pandas_gbq : None pyarrow : 14.0.1 pyreadstat : None python-calamine : None pyxlsb : None s3fs : None scipy : 1.11.4 sqlalchemy : None tables : None tabulate : None xarray : None xlrd : None zstandard : None tzdata : 2023.3 qtpy : None pyqt5 : None

[MarcoGorelli]

thanks @Andre-Medina for the report, this needs fixing, running a git bisect now

[MarcoGorelli]

From git bisect, this was introduced in #56767, @phofl

[phofl]

I am not sure that it is sensible to fix this, the new behavior aligns with DataFrame, which didn't support this before either.

dates.dt.round("30min")

That's what you want to do, we can fix this theoretically, but we should address the dataframe behavior as well then

[valeriupredoi]

hello :panda_face: folks, you guys gonna fix this in 2.2.3 please? Cheers muchly :beer:

[Andre-Medina]

re-raised this issue as it is still broken.