diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-01-11-01-10-11.bpo-1635741.7Haspf.rst b/Misc/NEWS.d/next/Core and Builtins/2022-01-11-01-10-11.bpo-1635741.7Haspf.rst
new file mode 100644
index 00000000000000..08b13c6fdabb7e
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-01-11-01-10-11.bpo-1635741.7Haspf.rst	
@@ -0,0 +1 @@
+Port _datetime extension module to multiphase initialization(:pep:`489`).
\ No newline at end of file
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index fda8401b84cd15..0cc3ca41ee9cc6 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -6694,27 +6694,27 @@ _datetime_exec(PyObject *module)
     return 0;
 }
 
+static struct PyModuleDef_Slot _datetime_slots[] = {
+    {Py_mod_exec, _datetime_exec},
+    {0, NULL}
+};
+
+PyDoc_STRVAR(module_doc,
+"Fast implementation of the datetime type.");
+
 static struct PyModuleDef datetimemodule = {
     PyModuleDef_HEAD_INIT,
     .m_name = "_datetime",
-    .m_doc = "Fast implementation of the datetime type.",
-    .m_size = -1,
+    .m_doc = module_doc,
+    .m_size = 0,
     .m_methods = module_methods,
+    .m_slots = _datetime_slots,
 };
 
 PyMODINIT_FUNC
 PyInit__datetime(void)
 {
-    PyObject *mod = PyModule_Create(&datetimemodule);
-    if (mod == NULL)
-        return NULL;
-
-    if (_datetime_exec(mod) < 0) {
-        Py_DECREF(mod);
-        return NULL;
-    }
-
-    return mod;
+    return PyModuleDef_Init(&datetimemodule);
 }
 
 /* ---------------------------------------------------------------------------