How To Set Time Prompt in SQLPLUS

We need to modify the glogin.sql sql file which will be located under $ORACLE_HOME/sqlplus/admin.
Take the backup of the glogin.sql and add the below entry.

set lines 200
set pages 200
set termout off
col dbname new_value prompt_dbname
select substr(global_name,1,instr(global_name,'.')-1) dbname
from global_name;
set sqlprompt "&&prompt_dbname> "
set termout on
set time on