JDBC client sends command to setup session when physical connection is established via a modified AUTH_ALTER_SESSION OCI attribute in the authentication phase.
If the JVM time zone is one of the magic constants in the oracle.sql.ZONEIDMAP class and oracle.jdbc.timezoneAsRegion = true (default) then AUTH_ALTER_SESSION looks like this (where Etc/UTC is the default timezone picked up by the JVM)
ALTER SESSION SET TIME_ZONE='Etc/UTC' NLS_LANGUAGE='POLISH' NLS_TERRITORY='POLAND'
which can fail with
ORA-01882: timezone region not found
01882. 00000 - "timezone region not found"
when given timezone id is not supported by server (see V$TIMEZONE_NAMES)
There are several solutions.
The first one is setting oracle.jdbc.timezoneAsRegion = false as the connection parameter or virtual machine property (-Doracle.jdbc.timezoneAsRegion=false). Then the query modifying the session turns to this
ALTER SESSION SET TIME_ZONE='+0:00' NLS_LANGUAGE='POLISH' NLS_TERRITORY='POLAND'
The second solution is to change the JVM time zone with the user.timezone parameter to timezone that is equivalent to what you need and supported by databse
e.g. -Duser.timezone=UTC or even -Duser.timezone=Etc/GMT.
The V$TIMEZONE_FILE view displays the zone file version being used by the database.
SELECT FILENAME,VERSION from V$TIMEZONE_FILE;
FILENAME VERSION
-------------------- ----------
timezlrg_14.dat 14
Time zone file can be upgraded: https://oracle-base.com/articles/misc/update-database-time-zone-file