python
diff --git a/‎Lib/test/test_capi/test_misc.py
Lines changed: 16 additions & 0 deletions b/‎Lib/test/test_capi/test_misc.py
Lines changed: 16 additions & 0 deletions
diff --git a/‎Modules/_testmultiphase.c
8000
Lines changed: 59 additions & 0 deletions b/‎Modules/_testmultiphase.c
8000
Lines changed: 59 additions & 0 deletions
@@ -2203,6 +2203,22 @@ def test_module_state_shared_in_global(self):
         subinterp_attr_id = os.read(r, 100)
         self.assertEqual(main_attr_id, subinterp_attr_id)
 
+    @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+    def test_datetime_capi_client(self):
+        script = textwrap.dedent("""
+            import importlib.machinery
+            import importlib.util
+            fullname = '_test_datetime_capi_client'
+            origin = importlib.util.find_spec('_testmultiphase').origin
+            loader = importlib.machinery.ExtensionFileLoader(fullname, origin)
+            spec = importlib.util.spec_from_loader(fullname, loader)
+            module = importlib.util.module_from_spec(spec)
+            spec.loader.exec_module(module)
+        """)
+        exec(script)  # run main interp first
+        ret = support.run_in_subinterp(script)
+        self.assertEqual(ret, 0)
+
 
 @requires_subinterpreters
 class InterpreterConfigTests(unittest.TestCase):
 
@@ -952,3 +952,62 @@ PyInit__test_shared_gil_only(void)
 {
     return PyModuleDef_Init(&shared_gil_only_def);
 }
+
+
+#include "datetime.h"
+
+static int
+datetime_capi_client_exec(PyObject *m)
+{
+    int ismain = PyInterpreterState_Get() == PyInterpreterState_Main();
+    if (ismain) {
+        _pydatetimeapi_main = NULL;
+    }
+
+    PyDateTime_IMPORT;
+    if (Py
10000
DateTimeAPI == NULL) {
+        return -1;
+    }
+    if (PyDateTimeAPI != PyCapsule_Import(PyDateTime_CAPSULE_NAME, 0)) {
+        return -1;
+    }
+    if (ismain) {
+        if (PyDateTimeAPI != _pydatetimeapi_main) {
+            return -1;
+        }
+    }
+    else {
+        if (PyDateTimeAPI == _pydatetimeapi_main) {
+            PyObject *module = PyImport_ImportModule("_datetime");
+            if (module == NULL) {
+                return -1;
+            }
+            PyModuleDef *def = PyModule_GetDef(module);
+            Py_DECREF(module);
+            if (def) {
+                // multi-phase init
+                return -1;
+            }
+            else {
+                // legacy init (shared module)
+                return 0;
+            }
+        }
+    }
+    return 0;
+}
+
+static PyModuleDef_Slot datetime_capi_client_slots[] = {
+    {Py_mod_exec, datetime_capi_client_exec},
+    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
+    {0, NULL},
+};
+
+static PyModuleDef datetime_capi_client_def = TEST_MODULE_DEF(
+    "_testmultiphase_datetime_capi_client", datetime_capi_client_slots, NULL);
+
+PyMODINIT_FUNC
+PyInit__test_datetime_capi_client(void)
+{
+    return PyModuleDef_Init(&datetime_capi_client_def);
+}