strange error after changing timezone

Greetings

I have setup a graphite server and i am currently feeding him some nginx stats with collectd. Intially everything is working as it should with the only issue been thus that i cannot see any stats when setting the graphs to "display last 1 minute". I thought that the problem may caused because the graphs have wrong time hence i went and changed the below values:

1) vim /opt/graphite/webapp/graphite/local_settings.py
 added: TIME_ZONE = 'Europe/Greece'

2) vim /opt/graphite/webapp/graphite/settings.py
 added: TIME_ZONE = 'Europe/Greece'

I restarted carbon-cache and when i vizited the dashboard there were no more graphs and no stats received by collect d. I decided to comment in again the above changes and bring the settings on those two files back to their initial state. I restarted graphite and when visited the dashboard i now get an internal server error from apache. (without any indicatons from error.log)

I HAVE REPLICATED THE ABOVE BY STARTING A FRESH INSTALL ON A FRESH UBUNTU MACHINE VM AND RESULTS ARE THE SAME. Meaning, i install graphite,/collectd and everything is working fine. I setup the time zone and then there are no stats on the graphs. I comment in the time zone and then there is internal server error.

Any help would be appriciated

Thanks