Performance of maybe_box_datetimelike #30520

pandas/core/common.py

@@ -84,9 +84,11 @@ def maybe_box(indexer, values, obj, key):
 def maybe_box_datetimelike(value):
     # turn a datetime like into a Timestamp/timedelta as needed
 
-    if isinstance(value, (np.datetime64, datetime)):
+    if isinstance(value, (np.datetime64, datetime)) \
+            and not isinstance(value, tslibs.Timestamp):
         value = tslibs.Timestamp(value)
-    elif isinstance(value, (np.timedelta64, timedelta)):
+    elif isinstance(value, (np.timedelta64, timedelta)) \
+            and not isinstance(value, tslibs.Timedelta):
         value = tslibs.Timedelta(value)
 
     return value