If timezone is not set at the JVM level, then JVM would default to use operating system’s timezone. It’s not a recommended practice to use Operating System’s time zone for the following reasons:
1. If your application is running across multiple data centers, say San Francisco, Chicago, Singapore – then JVMs in each data center would end up having different timezone. Thus JVMs in each data center would exhibit different behaviors. It would result in inconsistent results.
2. If you are deploying your application in cloud environment, applications could be moved to different data centers without your knowledge. In that circumstance also your application would end up producing different results.
3. Your own Operations team can also change the timezone, with out bringing to development team’s knowledge. It would also skew the results.
To avoid these commotion, it’s highly recommended to set timezone at the JVM. user.timezone system property is used to set timezone for the JVM. Example if you want to set EDT timezone for your application, you would do: