JVM TimeZone Configuration

When working with time and date values in Java, the timezone plays a crucial role in ensuring accuracy. However, discrepancies can arise when the JVM's default timezone does not align with the OS-specified timezone.

To address this issue, you can leverage the -Duser.timezone parameter when launching the JVM. By specifying the correct timezone, you can override the default GMT timezone and ensure the JVM adheres to your OS's settings.

For instance, consider the following scenario:

import java.util.Calendar;

public class DateTest {
    public static void main(String[] args) {
        Calendar now = Calendar.getInstance();
        System.out.println(now.getTimeZone());
        System.out.println(now.getTime());
    }
}

When this program is run, it displays the default GMT timezone and the corresponding date and time:

sun.util.calendar.ZoneInfo[id="GMT", offset=0, ...]
Mon Mar 22 13:46:45 GMT 2010

To set the JVM timezone to match the OS's settings, append the -Duser.timezone parameter to the JVM invocation:

java -Duser.timezone=Europe/Sofia DateTest

This will override the default GMT timezone and use the "Europe/Sofia" timezone instead, aligning with the OS's specification. You can replace "Europe/Sofia" with the appropriate timezone identifier for your system.

Alternatively, on Linux systems, you can set the TZ environment variable to specify the timezone:

export TZ=Europe/Sofia
java DateTest

By properly configuring the JVM timezone using these methods, you can ensure that your Java programs accurately reflect the time and date values according to your OS's settings.