diff --git a/js/src/jsdate.cpp b/js/src/jsdate.cpp
index d9a3c7d1abf1..4934446147cc 100644
--- a/js/src/jsdate.cpp
+++ b/js/src/jsdate.cpp
@@ -521,23 +521,6 @@ date_convert(JSContext *cx, HandleObject obj, JSType hint, MutableHandleValue vp
     return DefaultValue(cx, obj, (hint == JSTYPE_VOID) ? JSTYPE_STRING : hint, vp);
 }
 
-/*
- * Other Support routines and definitions
- */
-
-const Class DateObject::class_ = {
-    js_Date_str,
-    JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS) |
-    JSCLASS_HAS_CACHED_PROTO(JSProto_Date),
-    JS_PropertyStub,         /* addProperty */
-    JS_DeletePropertyStub,   /* delProperty */
-    JS_PropertyStub,         /* getProperty */
-    JS_StrictPropertyStub,   /* setProperty */
-    JS_EnumerateStub,
-    JS_ResolveStub,
-    date_convert
-};
-
 /* for use by date_parse */
 
 static const char* const wtb[] = {
@@ -3027,52 +3010,48 @@ js_Date(JSContext *cx, unsigned argc, Value *vp)
     return true;
 }
 
-JSObject *
-js_InitDateClass(JSContext *cx, HandleObject obj)
+static bool
+FinishDateClassInit(JSContext *cx, HandleObject ctor, HandleObject proto)
 {
-    JS_ASSERT(obj->isNative());
-
-    Rooted<GlobalObject*> global(cx, &obj->as<GlobalObject>());
-
-    RootedObject dateProto(cx, global->createBlankPrototype(cx, &DateObject::class_));
-    if (!dateProto)
-        return nullptr;
-    dateProto->as<DateObject>().setUTCTime(GenericNaN());
-
-    RootedFunction ctor(cx);
-    ctor = global->createConstructor(cx, js_Date, cx->names().Date, MAXARGS);
-    if (!ctor)
-        return nullptr;
-
-    if (!LinkConstructorAndPrototype(cx, ctor, dateProto))
-        return nullptr;
-
-    if (!DefinePropertiesAndBrand(cx, ctor, nullptr, date_static_methods))
-        return nullptr;
+    proto->as<DateObject>().setUTCTime(GenericNaN());
 
     /*
-     * Define all Date.prototype.* functions, then brand for trace-jitted code.
      * Date.prototype.toGMTString has the same initial value as
      * Date.prototype.toUTCString.
      */
-    if (!JS_DefineFunctions(cx, dateProto, date_methods))
-        return nullptr;
     RootedValue toUTCStringFun(cx);
     RootedId toUTCStringId(cx, NameToId(cx->names().toUTCString));
     RootedId toGMTStringId(cx, NameToId(cx->names().toGMTString));
-    if (!baseops::GetProperty(cx, dateProto, toUTCStringId, &toUTCStringFun) ||
-        !baseops::DefineGeneric(cx, dateProto, toGMTStringId, toUTCStringFun,
-                                JS_PropertyStub, JS_StrictPropertyStub, 0))
-    {
-        return nullptr;
-    }
-
-    if (!DefineConstructorAndPrototype(cx, global, JSProto_Date, ctor, dateProto))
-        return nullptr;
-
-    return dateProto;
+    return baseops::GetProperty(cx, proto, toUTCStringId, &toUTCStringFun) &&
+           baseops::DefineGeneric(cx, proto, toGMTStringId, toUTCStringFun,
+                                  JS_PropertyStub, JS_StrictPropertyStub, 0);
 }
 
+const Class DateObject::class_ = {
+    js_Date_str,
+    JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS) |
+    JSCLASS_HAS_CACHED_PROTO(JSProto_Date),
+    JS_PropertyStub,         /* addProperty */
+    JS_DeletePropertyStub,   /* delProperty */
+    JS_PropertyStub,         /* getProperty */
+    JS_StrictPropertyStub,   /* setProperty */
+    JS_EnumerateStub,
+    JS_ResolveStub,
+    date_convert,
+    nullptr,                 /* finalize */
+    nullptr,                 /* call */
+    nullptr,                 /* hasInstance */
+    nullptr,                 /* construct */
+    nullptr,                 /* trace */
+    {
+        GenericCreateConstructor<js_Date, NAME_OFFSET(Date), MAXARGS>,
+        GenericCreatePrototype<&DateObject::class_>,
+        date_static_methods,
+        date_methods,
+        FinishDateClassInit
+    }
+};
+
 JS_FRIEND_API(JSObject *)
 js_NewDateObjectMsec(JSContext *cx, double msec_time)
 {
diff --git a/js/src/jsdate.h b/js/src/jsdate.h
index 028e64794e4a..5a033174ef91 100644
--- a/js/src/jsdate.h
+++ b/js/src/jsdate.h
@@ -16,9 +16,6 @@
 #include "js/RootingAPI.h"
 #include "js/TypeDecls.h"
 
-extern JSObject *
-js_InitDateClass(JSContext *cx, JS::HandleObject obj);
-
 /*
  * These functions provide a C interface to the date/time object
  */
diff --git a/js/src/jsprototypes.h b/js/src/jsprototypes.h
index 91fdffc7a81d..f85f30782f08 100644
--- a/js/src/jsprototypes.h
+++ b/js/src/jsprototypes.h
@@ -61,7 +61,7 @@
     real(Array,                  3,     js_InitArrayClass,         OCLASP(Array)) \
     real(Boolean,                4,     js_InitBooleanClass,       OCLASP(Boolean)) \
     real(JSON,                   5,     js_InitJSONClass,          CLASP(JSON)) \
-    real(Date,                   6,     js_InitDateClass,          OCLASP(Date)) \
+    real(Date,                   6,     js_InitViaClassSpec,       OCLASP(Date)) \
     real(Math,                   7,     js_InitMathClass,          CLASP(Math)) \
     real(Number,                 8,     js_InitNumberClass,        OCLASP(Number)) \
     real(String,                 9,     js_InitStringClass,        OCLASP(String)) \