diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7c0e038ebf5..eb0f61dd4b5 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -14539,10 +14539,20 @@ a_expr:		c_expr									{ $$ = $1; }
 				}
 			| a_expr AT TIME ZONE a_expr			%prec AT
 				{
-					$$ = (Node *) makeFuncCall(SystemFuncName("timezone"),
-											   list_make2($5, $1),
-											   COERCE_SQL_SYNTAX,
-											   @2);
+					if(sql_dialect == SQL_DIALECT_TSQL)
+					{
+						$$ = (Node *) makeFuncCall(list_make2(makeString("sys"), makeString("timezone")),
+													list_make2($5, $1),
+													COERCE_SQL_SYNTAX,
+													@2);
+					}
+					else
+					{
+						$$ = (Node *) makeFuncCall(SystemFuncName("timezone"),
+													list_make2($5, $1),
+													COERCE_SQL_SYNTAX,
+													@2);
+					}
 				}
 		/*
 		 * These operators must be called out explicitly in order to make use