Oracle RAC requires that all cluster nodes have the same time zone setting.

During an Oracle Grid Infrastructure for a cluster installation, the installation process determines the time zone setting of the Grid installation owner on the node where Oracle Universal Installer (OUI) runs. OUI uses that time zone value on all of the nodes as the default time zone setting for all processes that Oracle Clusterware manages. This default setting is used for databases, Oracle ASM, and any other managed processes. However, if you start an instance with SQL*Plus, you must ensure that the time zone value that Oracle RAC uses is the same as the Oracle Clusterware time zone. You can change the time zone that Oracle Clusterware uses for a database by running the command srvctl setenv database -env 'TZ=time zone'