address comments

Author: Neenu1995

java-bigquery/google-cloud-bigquery-jdbc/.gitignore

@@ -2,6 +2,7 @@ drivers/**
 target-it/**
 *logs*/**
 **/ITBigQueryJDBCLocalTest.java
+**/BigQueryStatementE2EBenchmark.java
 
 tools/**/*.class
 tools/**/*.jfr

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/jdbc/BigQueryTypeCoercionUtility.java

@@ -200,7 +200,9 @@ public Time coerce(Long value) {
       // Note: BQ Time has a precision of up to six fractional digits (microsecond precision)
       // but java.sql.Time only supports up to millisecond precision. So data after milliseconds is
       // truncated.
-      return new Time(value / 1000);
+      long millisOfDay = value / 1000;
+      long localMillis = TimeZoneCache.getLocalMillis(millisOfDay);
+      return new Time(localMillis);
     }
   }
 
@@ -209,7 +211,7 @@ private static class LongToTimestamp implements BigQueryCoercion<Long, Timestamp
     @Override
     public Timestamp coerce(Long value) {
       // Long value is in microseconds. All further calculations should account for the unit.
-      Instant instant = Instant.ofEpochMilli(value / 1000).plusNanos((value % 1000) * 1000);
+      Instant instant = Instant.EPOCH.plus(value, ChronoUnit.MICROS);
       // Timezone-agnostic conversion preserving exact point in time as mandated by JDBC spec
       return Timestamp.from(instant);
     }
@@ -252,7 +254,7 @@ public Time coerce(FieldValue fieldValue) {
         long millisOfDay = TimeUnit.NANOSECONDS.toMillis(localTime.toNanoOfDay());
         // Adjust by local timezone offset to ensure correct wall-clock representation with
         // millisecond precision
-        long localMillis = millisOfDay - java.util.TimeZone.getDefault().getOffset(millisOfDay);
+        long localMillis = TimeZoneCache.getLocalMillis(millisOfDay);
         return new Time(localMillis);
       } catch (java.time.format.DateTimeParseException e) {
         IllegalArgumentException ex =

java-bigquery/google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/jdbc/TimeZoneCache.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.bigquery.jdbc;
+
+import com.google.api.core.InternalApi;
+import java.util.TimeZone;
+
+@InternalApi
+public class TimeZoneCache {
+  private static volatile TimeZone defaultTimeZone = TimeZone.getDefault();
+
+  public static void reset() {
+    defaultTimeZone = TimeZone.getDefault();
+  }
+
+  public static long getLocalMillis(long millisOfDay) {
+    return millisOfDay - defaultTimeZone.getOffset(millisOfDay);
+  }
+}

java-bigquery/google-cloud-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/ArrowFormatTypeBigQueryCoercionUtilityTest.java

@@ -164,8 +164,28 @@ public void nullToTime() {
 
   @Test
   public void longToTime() {
-    assertThat(INSTANCE.coerceTo(Time.class, 1408452095220000L))
-        .isEqualTo(new Time(1408452095220L));
+    long value = 1408452095220000L;
+    // 1408452095220000 microseconds is 1408452095220 milliseconds.
+    // Since the test runs under UTC timezone by TimeZoneRule, expected localMillis is
+    // 1408452095220L.
+    assertThat(INSTANCE.coerceTo(Time.class, value)).isEqualTo(new Time(1408452095220L));
+  }
+
+  @Test
+  public void longToTimeInNonUTCTimeZone() {
+    java.util.TimeZone originalTimeZone = java.util.TimeZone.getDefault();
+    try {
+      java.util.TimeZone.setDefault(java.util.TimeZone.getTimeZone("America/Los_Angeles"));
+      com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
+      long value = 1408452095220000L;
+      // 1408452095220000 microseconds is 1408452095220 milliseconds.
+      // Under America/Los_Angeles (PDT, -7 hours offset in Aug 2014), the subtracted offset
+      // results in 1408452095220 - (-25200000) = 1408477295220L.
+      assertThat(INSTANCE.coerceTo(Time.class, value)).isEqualTo(new Time(1408477295220L));
+    } finally {
+      java.util.TimeZone.setDefault(originalTimeZone);
+      com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
+    }
   }
 
   @Test

java-bigquery/google-cloud-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/FieldValueTypeBigQueryCoercionUtilityTest.java

@@ -29,6 +29,7 @@
 import com.google.cloud.bigquery.FieldValueList;
 import com.google.cloud.bigquery.Range;
 import com.google.cloud.bigquery.exception.BigQueryJdbcCoercionException;
+import com.google.cloud.bigquery.jdbc.rules.TimeZoneRule;
 import com.google.common.collect.ImmutableList;
 import java.math.BigDecimal;
 import java.sql.Date;
@@ -38,10 +39,12 @@
 import java.time.LocalDate;
 import java.time.LocalTime;
 import java.time.temporal.ChronoUnit;
-import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
 
 public class FieldValueTypeBigQueryCoercionUtilityTest {
+  @RegisterExtension public final TimeZoneRule timeZoneRule = new TimeZoneRule("UTC");
+
   private static final FieldValue STRING_VALUE = FieldValue.of(PRIMITIVE, "sample-string");
   private static final FieldValue INTEGER_VALUE = FieldValue.of(PRIMITIVE, "345");
   private static final FieldValue FLOAT_VALUE = FieldValue.of(PRIMITIVE, "345.21");
@@ -315,11 +318,27 @@ public void fieldValueToTimestampWhenInnerValueIsNull() {
   public void fieldValueToTime() {
     LocalTime expectedTime = LocalTime.of(23, 59, 59);
     assertThat(INSTANCE.coerceTo(Time.class, TIME_VALUE)).isEqualTo(Time.valueOf(expectedTime));
-    LocalTime expectedTimeWithNanos = LocalTime.parse("23:59:59.99999");
-    long millisOfDay = TimeUnit.NANOSECONDS.toMillis(expectedTimeWithNanos.toNanoOfDay());
-    long localMillis = millisOfDay - java.util.TimeZone.getDefault().getOffset(millisOfDay);
+    // expectedTimeWithNanos has 999 milliseconds, giving 86399999 ms of day.
+    // Since the test runs under UTC timezone by TimeZoneRule, expected localMillis is 86399999L.
     assertThat(INSTANCE.coerceTo(Time.class, TIME_WITH_NANOSECOND_VALUE))
-        .isEqualTo(new Time(localMillis));
+        .isEqualTo(new Time(86399999L));
+  }
+
+  @Test
+  public void fieldValueToTimeInNonUTCTimeZone() {
+    java.util.TimeZone originalTimeZone = java.util.TimeZone.getDefault();
+    try {
+      java.util.TimeZone.setDefault(java.util.TimeZone.getTimeZone("America/Los_Angeles"));
+      com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
+      // 23:59:59.99999 yields 86399999 milliseconds.
+      // Under America/Los_Angeles on 1970-01-01 (PST, -8 hours offset),
+      // the subtracted offset results in 86399999 - (-28800000) = 115199999L.
+      assertThat(INSTANCE.coerceTo(Time.class, TIME_WITH_NANOSECOND_VALUE))
+          .isEqualTo(new Time(115199999L));
+    } finally {
+      java.util.TimeZone.setDefault(originalTimeZone);
+      com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
+    }
   }
 
   @Test

java-bigquery/google-cloud-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/rules/TimeZoneRule.java

@@ -37,11 +37,13 @@ public TimeZoneRule(String timeZoneId) {
   public void beforeAll(ExtensionContext context) {
     defaultTimeZone = TimeZone.getDefault();
     TimeZone.setDefault(TimeZone.getTimeZone(timeZoneId));
+    com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
   }
 
   @Override
   public void afterAll(ExtensionContext context) {
     TimeZone.setDefault(defaultTimeZone);
+    com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
   }
 
   @Override
@@ -50,17 +52,20 @@ public void beforeEach(ExtensionContext context) {
       defaultTimeZone = TimeZone.getDefault();
     }
     TimeZone.setDefault(TimeZone.getTimeZone(timeZoneId));
+    com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
   }
 
   @Override
   public void afterEach(ExtensionContext context) {
     if (defaultTimeZone != null) {
       TimeZone.setDefault(defaultTimeZone);
     }
+    com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
   }
 
   /** Public method to enforce the rule manually */
   public void enforce() {
     TimeZone.setDefault(TimeZone.getTimeZone(timeZoneId));
+    com.google.cloud.bigquery.jdbc.TimeZoneCache.reset();
   }
 }