BUG: `date_range` gives different output ends for fixed `end` and varying `start` when `freq="B"`

[torext]

Pandas version checks

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

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

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

Reproducible Example

import datetime as dt

import pandas as pd

end = dt.datetime(2025, 7, 26, 6)  # Saturday early morning
for d in range(18, 22):  # Friday, Saturday, Sunday & Monday
    start = dt.datetime(2025, 7, d, 10)
    print(f"start={start}: {pd.date_range(start, end, freq="B")}\n")

Issue Description

Running date_range with varying start and fixed end gives outputs differing final entries when freq="B". Specifically, in the above example, the first and last iteration are missing an entry for 2025-07-25 10:00:00.

Expected Behavior

The last three iterations in the above code should produce the same output, and the first iteration should differ from the other three only in that it additionally includes 2025-07-18 10:00:00 as a first entry. Instead the output is the following:

start=2025-07-18 10:00:00: DatetimeIndex(['2025-07-18 10:00:00', '2025-07-21 10:00:00',
               '2025-07-22 10:00:00', '2025-07-23 10:00:00',
               '2025-07-24 10:00:00'],
              dtype='datetime64[ns]', freq='B')

start=2025-07-19 10:00:00: DatetimeIndex(['2025-07-21 10:00:00', '2025-07-22 10:00:00',
               '2025-07-23 10:00:00', '2025-07-24 10:00:00',
               '2025-07-25 10:00:00'],
              dtype='datetime64[ns]', freq='B')

start=2025-07-20 10:00:00: DatetimeIndex(['2025-07-21 10:00:00', '2025-07-22 10:00:00',
               '2025-07-23 10:00:00', '2025-07-24 10:00:00',
               '2025-07-25 10:00:00'],
              dtype='datetime64[ns]', freq='B')

start=2025-07-21 10:00:00: DatetimeIndex(['2025-07-21 10:00:00', '2025-07-22 10:00:00',
               '2025-07-23 10:00:00', '2025-07-24 10:00:00'],
              dtype='datetime64[ns]', freq='B')

Installed Versions

INSTALLED VERSIONS

commit : 0691c5c
python : 3.12.9
python-bits : 64
OS : Linux
OS-release : 4.18.0-553.36.1.el8_10.x86_64
Version : #1 SMP Wed Jan 22 03:07:54 EST 2025
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.2.3
numpy : 2.1.3
pytz : 2024.1
dateutil : 2.9.0.post0
pip : 25.0.1
Cython : None
sphinx : None
IPython : 9.1.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.13.3
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : 2025.3.2
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.6
lxml.etree : 5.3.2
matplotlib : 3.10.1
numba : 0.61.0
numexpr : 2.10.2
odfpy : None
openpyxl : 3.1.5
pandas_gbq : None
psycopg2 : 2.9.9
pymysql : None
pyarrow : 17.0.0
pyreadstat : None
pytest : 8.3.5
python-calamine : None
pyxlsb : None
s3fs : 2025.3.2
scipy : 1.15.2
sqlalchemy : 2.0.40
tables : 3.10.2
tabulate : 0.9.0
xarray : None
xlrd : None
xlsxwriter : None
zstandard : 0.23.0
tzdata : 2025.2
qtpy : None
pyqt5 : None

[torext]

It looks like this very old issue #35342 might be related to this, as in addition to the example I gave above I've observed other variations of it where the output is expected etc.

[rhshadrach]

Thanks for the report! I am seeing all end on 2025-07-25 10:00:00 on main. There are a number of fixes in this regard coming in 3.0; closing.