I have however setup the appropriate time zone in the sqldeveloper.conf file but am still get the same error below.
So you 'did something' and what you 'did' doesn't work and you want help with what you 'did'?
The post the 'something' you 'did' so we can see what you 'did' wrong. That exception generally means that what you 'did' was NOT an 'appropriate time zone'.
Thank you Gary.
It turns out that I placed the timezone setting in the wrong part of the config file.