DOC: Correct inconsistent description on default DateOffset setting (#36516)

* Update timeseries.rst

correct inconsistent doc description on default DateOffset setting

* Update timeseries.rst

remove the example for DateOffset default setting

* Update offsets.pyx

Change the default setting for DateOffset to a calendar day.

* Update test_liboffsets.py

add a test for dateoffset default value

* Update timeseries.rst

change doc to original description

* Update test_liboffsets.py

resolve PEP 8 issues

* Update timeseries.rst

* Update test_liboffsets.py

* Update offsets.pyx

* Change default Offset setting description in DOC

* Update timeseries.rst

* Update timeseries.rst

Author: GYHHAHA

doc/source/user_guide/timeseries.rst

@@ -879,7 +879,7 @@ into ``freq`` keyword arguments. The available date offsets and associated frequ
     :header: "Date Offset", "Frequency String", "Description"
     :widths: 15, 15, 65
 
-    :class:`~pandas.tseries.offsets.DateOffset`, None, "Generic offset class, defaults to 1 calendar day"
+    :class:`~pandas.tseries.offsets.DateOffset`, None, "Generic offset class, defaults to absolute 24 hours"
     :class:`~pandas.tseries.offsets.BDay` or :class:`~pandas.tseries.offsets.BusinessDay`, ``'B'``,"business day (weekday)"
     :class:`~pandas.tseries.offsets.CDay` or :class:`~pandas.tseries.offsets.CustomBusinessDay`, ``'C'``, "custom business day"
     :class:`~pandas.tseries.offsets.Week`, ``'W'``, "one week, optionally anchored on a day of the week"