Make timezone setting in logging to be explicit

NEXT_CHANGELOG.md

@@ -9,12 +9,14 @@
 ### Updated
 - Added validation for positive integer configuration properties (RowsFetchedPerBlock, BatchInsertSize, etc.) to prevent hangs and errors when set to zero or negative values.
 - Updated Circuit breaker to be triggered by 429 errors too.
+- Log timestamps now explicitly display timezone.
 
 ### Fixed
 
 - Fix driver crash when using `INTERVAL` types.
 - Fix connection failure in restricted environments when `LogLevel.OFF` is used.
 - Fix U2M by including SDK OAuth HTML callback resources.
+- Remove global JVM timezone modification from `Driver.main()` to prevent side effects on other code running in the same JVM.
 
 ---
 *Note: When making changes, please add your change under the appropriate section with a brief description.*

src/main/java/com/databricks/client/jdbc/Driver.java

@@ -21,7 +21,6 @@
 import java.sql.SQLException;
 import java.util.List;
 import java.util.Properties;
-import java.util.TimeZone;
 import java.util.concurrent.CompletableFuture;
 import java.util.logging.Logger;
 
@@ -39,8 +38,6 @@ public class Driver implements IDatabricksDriver {
   }
 
   public static void main(String[] args) {
-    TimeZone.setDefault(
-        TimeZone.getTimeZone("UTC")); // Logging, timestamps are in UTC across the application
     System.out.printf("The driver {%s} has been initialized.%n", Driver.class);
   }
 

src/main/java/com/databricks/jdbc/log/Slf4jFormatter.java

@@ -2,7 +2,6 @@
 
 import java.text.SimpleDateFormat;
 import java.util.Date;
-import java.util.TimeZone;
 import java.util.logging.Formatter;
 import java.util.logging.LogRecord;
 
@@ -12,13 +11,12 @@
  */
 public class Slf4jFormatter extends Formatter {
 
-  private static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
+  private static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss z";
 
   private static final SimpleDateFormat dateFormat;
 
   static {
     dateFormat = new SimpleDateFormat(DATE_FORMAT);
-    dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
   }
 
   /** {@inheritDoc} */

src/test/java/com/databricks/jdbc/log/Slf4jFormatterTest.java

@@ -23,24 +23,29 @@ public void setUp() {
 
   @Test
   public void testFormat() {
-    // Create a sample LogRecord
     LogRecord record = new LogRecord(Level.INFO, "Test message");
     record.setSourceClassName("TestClass");
     record.setSourceMethodName("testMethod");
 
-    // Set a specific timestamp for testing
     Instant instant = Instant.parse("2021-07-01T00:00:00Z");
     record.setInstant(instant);
 
-    // Format the log record
     String formattedLog = formatter.format(record);
 
-    // Expected format: "yyyy-MM-dd HH:mm:ss LEVEL ClassName#methodName - message"
+    // Use system default timezone (matches formatter)
+    TimeZone formatterZone = TimeZone.getDefault();
+
     SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
-    dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
+    dateFormat.setTimeZone(formatterZone);
+
     String expectedTimestamp = dateFormat.format(Date.from(instant));
+
+    // Use SHORT display name instead of ID (Asia/Kolkata → IST)
+    String expectedZone = formatterZone.getDisplayName(false, TimeZone.SHORT);
+
     String expected =
-        String.format("%s INFO TestClass#testMethod - Test message%n", expectedTimestamp);
+        String.format(
+            "%s %s INFO TestClass#testMethod - Test message%n", expectedTimestamp, expectedZone);
 
     assertEquals(expected, formattedLog);
   }