REGR: Index.map converting tz-agnostic result to tz

Author: rhshadrach

pandas/core/indexes/base.py

@@ -6124,14 +6124,16 @@ def map(self, mapper, na_action: Literal["ignore"] | None = None):
             # empty
             dtype = self.dtype
 
-        # e.g. if we are floating and new_values is all ints, then we
-        #  don't want to cast back to floating.  But if we are UInt64
-        #  and new_values is all ints, we want to try.
-        same_dtype = lib.infer_dtype(new_values, skipna=False) == self.inferred_type
-        if same_dtype:
-            new_values = maybe_cast_pointwise_result(
-                new_values, self.dtype, same_dtype=same_dtype
-            )
+        if self.inferred_type != "datetime64":
+            # e.g. if we are floating and new_values is all ints, then we
+            #  don't want to cast back to floating.  But if we are UInt64
+            #  and new_values is all ints, we want to try.
+            # GH#57192 - we skip datetime64 because inference from values is reliable
+            same_dtype = lib.infer_dtype(new_values, skipna=False) == self.inferred_type
+            if same_dtype:
+                new_values = maybe_cast_pointwise_result(
+                    new_values, self.dtype, same_dtype=same_dtype
+                )
 
         return Index._with_infer(new_values, dtype=dtype, copy=False, name=self.name)