This question was posed to me recently. As per Oracle, all instances which use 8i or above need to apply DB timezone patches version 4. Here's the quote from Oracle:
"It is not possible to automatically determine time zone use in a database. This is because timezone data is embedded not only in database tables, but also in arguments to user-defined procedures and functions (in both PL/SQL and Java). There is no way for Oracle to definitively tell any customer that they do NOT need to patch. "
So the answer is short and sweet. All ERP instances using RDBMS version 8i and above need to apply timezone patches version 4. Since the patch is very small, the downtime required is also small. You can piggyback this patch with your quarterly CPU or any of the weekend outages.
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