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Reproducible Example

import pandas as pd
pd.period_range('2000', periods=3, freq='M').to_timestamp('M')

Issue Description

The docs say

Cast to DatetimeIndex of timestamps, at beginning of period.

A Period(freq='M') starts at the beginning of the month, and ends on the last moment before the next month:

In [7]: pd.Period('2000', freq='M').start_time
Out[7]: Timestamp('2000-01-01 00:00:00')

In [8]: pd.Period('2000', freq='M').end_time
Out[8]: Timestamp('2000-01-31 23:59:59.999999999')

Expected Behavior

So, I'd have expected the above to output

DatetimeIndex(['2000-01-01', '2000-02-01', '2000-03-01'], dtype='datetime64[ns]', freq='MS')

Instead, we get

DatetimeIndex(['2000-01-31', '2000-02-29', '2000-03-31'], dtype='datetime64[ns]', freq='ME')

This looks odd. But, it's also been like that since as far back as I tested (i.e. pandas 0.25.3 😱 )

>>> import pandas as pd
>>> pd.period_range('2000', periods=3, freq='M').to_timestamp('M')
DatetimeIndex(['2000-01-31', '2000-02-29', '2000-03-31'], dtype='datetime64[ns]', freq='M')
>>> pd.__version__
'0.25.3'

Urgh, now what.

Splitting this off from https://github.com/pandas-dev/pandas/issues/58974

Installed Versions

INSTALLED VERSIONS ------------------ commit : b552dc95c9fa50e9ca2a0c9f9cdb8757f794fedb python : 3.10.12 python-bits : 64 OS : Linux OS-release : 5.15.153.1-microsoft-standard-WSL2 Version : #1 SMP Fri Mar 29 23:14:13 UTC 2024 machine : x86_64 processor : x86_64 byteorder : little LC_ALL : None LANG : C.UTF-8 LOCALE : en_US.UTF-8 pandas : 3.0.0.dev0+618.gb552dc95c9 numpy : 1.26.4 pytz : 2024.1 dateutil : 2.9.0.post0 pip : 24.0 Cython : 3.0.9 sphinx : 7.2.6 IPython : 8.22.2 adbc-driver-postgresql: None adbc-driver-sqlite : None bs4 : 4.12.3 blosc : None bottleneck : 1.3.8 fastparquet : 2024.2.0 fsspec : 2024.3.1 html5lib : 1.1 hypothesis : 6.99.13 gcsfs : 2024.3.1 jinja2 : 3.1.3 lxml.etree : 5.1.0 matplotlib : 3.8.3 numba : 0.59.1 numexpr : 2.9.0 odfpy : None openpyxl : 3.1.2 psycopg2 : 2.9.9 pymysql : 1.4.6 pyarrow : 16.1.0 pyreadstat : 1.2.7 pytest : 8.1.1 python-calamine : None pyxlsb : 1.0.10 s3fs : 2024.3.1 scipy : 1.12.0 sqlalchemy : 2.0.29 tables : 3.9.2 tabulate : 0.9.0 xarray : 2024.2.0 xlrd : 2.0.1 xlsxwriter : 3.2.0 zstandard : 0.22.0 tzdata : 2024.1 qtpy : None pyqt5 : None

Comment From: MarcoGorelli

I think this should be treated as a bug and just fixed in 3.0? will investigate more closely

Comment From: aram-cedarwood

take