BUG: to_datetime() warns unnecessarily that format cannot be inferred

[metazoic]

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

pd.to_datetime(['2020-01-01T20:20:20', '2020-01-01T20:21:20'])

Issue Description

This produces the following warning even though the format is inferable:

UserWarning: Could not infer format, so each element will be parsed individually, falling back to `dateutil`. To ensure parsing is consistent and as-expected, please specify a format.

Digging deeper, this warning occurs only when the year = concatenated hour and minute in the first element of the list, e.g. year = 2020, hour = 20, minute = 20.

Expected Behavior

to_datetime() should behave just as it does when this unique condition does not hold.

Installed Versions

INSTALLED VERSIONS

commit : 0691c5c
python : 3.12.9
python-bits : 64
OS : Darwin
OS-release : 24.3.0
Version : Darwin Kernel Version 24.3.0: Thu Jan 2 20:24:24 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T6030
machine : arm64
processor : arm
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
Cython : None
sphinx : 7.3.7
IPython : 8.30.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
blosc : None
bottleneck : 1.4.2
dataframe-api-compat : None
fastparquet : None
fsspec : 2024.12.0
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.6
lxml.etree : 5.3.0
matplotlib : 3.10.0
numba : 0.61.0
numexpr : 2.10.1
odfpy : None
openpyxl : 3.1.5
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : 19.0.0
pyreadstat : None
pytest : 8.3.4
python-calamine : None
pyxlsb : None
s3fs : 2024.12.0
scipy : 1.15.1
sqlalchemy : 2.0.37
tables : 3.10.2
tabulate : 0.9.0
xarray : 2024.11.0
xlrd : None
xlsxwriter : None
zstandard : 0.23.0
tzdata : 2023.3
qtpy : 2.4.1
pyqt5 : None

[asishm]

This seems to be fixed in main

[myenugula]

I've run your reproducible locally and it didn't give me any user warning.

Installed Versions

INSTALLED VERSIONS
------------------
commit                : 543680dcd9af5e4a9443d54204ec21e801652252
python                : 3.11.9
python-bits           : 64
OS                    : Darwin
OS-release            : 24.3.0
Version               : Darwin Kernel Version 24.3.0: Thu Jan  2 20:24:23 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T6031
machine               : arm64
processor             : arm
byteorder             : little
LC_ALL                : None
LANG                  : None
LOCALE                : en_US.UTF-8

pandas                : 0+untagged.36056.g543680d
numpy                 : 2.2.4
dateutil              : 2.9.0.post0
pip                   : 25.0.1
Cython                : 3.0.12
sphinx                : None
IPython               : None
adbc-driver-postgresql: None
adbc-driver-sqlite    : None
bs4                   : None
blosc                 : None
bottleneck            : None
fastparquet           : None
fsspec                : None
html5lib              : None
hypothesis            : None
gcsfs                 : None
jinja2                : None
lxml.etree            : None
matplotlib            : None
numba                 : None
numexpr               : None
odfpy                 : None
openpyxl              : None
psycopg2              : None
pymysql               : None
pyarrow               : None
pyreadstat            : None
pytest                : None
python-calamine       : None
pytz                  : 2025.2
pyxlsb                : None
s3fs                  : None
scipy                 : None
sqlalchemy            : None
tables                : None
tabulate              : None
xarray                : None
xlrd                  : None
xlsxwriter            : None
zstandard             : None
tzdata                : 2025.2
qtpy                  : None
pyqt5                 : None

[rhshadrach]

Thanks @asishm and @myenugula - closing.