This entry helps you change the database time zone: http://cloudconclave.blogspot.com/2013/08/aws-rds-timezone.html
However, it does not address changed the operating system time zone. With RDS, the OS timezone can’t be changed (UTC, by design). Each database engine supports different functions that query OS (for Oracle it is sysdate), database engine, or session level parameters for timezone information .
Here’s a quick synopsis of each DB engine’s datetime function details which identifies which calls are OS, database instance, or session based and which include timezone information or if its implied:
· SQL Server: http://msdn.microsoft.com/en-us/library/ms186724.aspx