REF: share some constructor code
- [ ] closes #xxxx (Replace xxxx with the Github issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

```
mypy.....................................................................Failed
- hook id: mypy
- exit code: 1
pandas/core/arrays/datetimelike.py:2054: error: Item "ndarray[Any, Any]" of "Union[ndarray[Any, Any], ExtensionArray]" has no attribute "categories"  [union-attr]
pandas/core/arrays/datetimelike.py:2054: error: Item "ExtensionArray" of "Union[ndarray[Any, Any], ExtensionArray]" has no attribute "categories"  [union-attr]
pandas/core/arrays/datetimelike.py:2054: error: Item "ndarray[Any, Any]" of "Union[ndarray[Any, Any], ExtensionArray]" has no attribute "codes"  [union-attr]
pandas/core/arrays/datetimelike.py:2054: error: Item "ExtensionArray" of "Union[ndarray[Any, Any], ExtensionArray]" has no attribute "codes"  [union-attr]
Found 4 errors in 1 file (checked 1392 source files)
``` fixed