diff --git a/core/src/main/java/org/apache/calcite/avatica/AvaticaSite.java b/core/src/main/java/org/apache/calcite/avatica/AvaticaSite.java
index 18e12f082..198fe03ce 100644
--- a/core/src/main/java/org/apache/calcite/avatica/AvaticaSite.java
+++ b/core/src/main/java/org/apache/calcite/avatica/AvaticaSite.java
@@ -37,6 +37,9 @@
 import java.sql.Time;
 import java.sql.Timestamp;
 import java.sql.Types;
+import java.time.*;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
 import java.util.Calendar;
 
 /**
@@ -500,21 +503,65 @@ private static byte[] toBytes(Object x) {
 
   private static Date toDate(Object x) {
     if (x instanceof String) {
-      return Date.valueOf((String) x);
+      String s = (String) x;
+
+      try {
+        LocalDate d = LocalDate.parse(s, DateTimeFormatter.ISO_LOCAL_DATE);
+        return Date.valueOf(d);
+      } catch (DateTimeParseException ignored) { }
+
+      try {
+        OffsetDateTime odt = OffsetDateTime.parse(s, DateTimeFormatter.ISO_OFFSET_DATE_TIME);
+        return Date.valueOf(odt.toLocalDate());
+      } catch (DateTimeParseException ignored) { }
+
+      try {
+        Instant instant = Instant.from(DateTimeFormatter.ISO_INSTANT.parse(s));
+        LocalDate d = instant.atZone(ZoneId.systemDefault()).toLocalDate();
+        return Date.valueOf(d);
+      } catch (DateTimeParseException | IllegalArgumentException ignored) { }
+
+      return Date.valueOf(s);
     }
     return new Date(toLong(x));
   }
 
   private static Time toTime(Object x) {
     if (x instanceof String) {
-      return Time.valueOf((String) x);
+      String s = (String) x;
+      try {
+        OffsetTime ot = OffsetTime.parse(s, DateTimeFormatter.ISO_OFFSET_TIME);
+        return Time.valueOf(ot.toLocalTime());
+      } catch (DateTimeParseException ignored) { }
+
+      try {
+        LocalTime lt = LocalTime.parse(s, DateTimeFormatter.ISO_LOCAL_TIME);
+        return Time.valueOf(lt);
+      } catch (DateTimeParseException ignored) { }
+
+      return Time.valueOf(s);
     }
     return new Time(toLong(x));
   }
 
   private static Timestamp toTimestamp(Object x) {
     if (x instanceof String) {
-      return Timestamp.valueOf((String) x);
+      String s = (String) x;
+      try {
+        ZonedDateTime zdt = ZonedDateTime.parse(s, DateTimeFormatter.ISO_ZONED_DATE_TIME);
+        return Timestamp.from(zdt.toInstant());
+      } catch (DateTimeParseException ignored) { }
+
+      try {
+        OffsetDateTime odt = OffsetDateTime.parse(s, DateTimeFormatter.ISO_OFFSET_DATE_TIME);
+        return Timestamp.from(odt.toInstant());
+      } catch (DateTimeParseException ignored) { }
+
+      try {
+        return Timestamp.valueOf(LocalDateTime.parse(s));
+      } catch (DateTimeParseException ignored) { }
+
+      return Timestamp.valueOf(s);
     }
     return new Timestamp(toLong(x));
   }
diff --git a/core/src/test/java/org/apache/calcite/avatica/AvaticaSiteTest.java b/core/src/test/java/org/apache/calcite/avatica/AvaticaSiteTest.java
new file mode 100644
index 000000000..f4cb5e5fb
--- /dev/null
+++ b/core/src/test/java/org/apache/calcite/avatica/AvaticaSiteTest.java
@@ -0,0 +1,71 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you 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
+ *
+ * http://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 org.apache.calcite.avatica;
+
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.sql.*;
+import java.time.Instant;
+
+import static org.junit.Assert.*;
+
+public class AvaticaSiteTest {
+  @Test
+  public void testToDateIsoAndJdbc() throws Exception {
+    Method toDate = org.apache.calcite.avatica.AvaticaSite.class.getDeclaredMethod("toDate",
+        Object.class);
+    toDate.setAccessible(true);
+
+    assertEquals(Date.valueOf("2025-04-01"), toDate.invoke(null, "2025-04-01"));
+    assertEquals(Date.valueOf("2025-04-01"), toDate.invoke(null, "2025-04-01T00:00:00Z"));
+    assertEquals(Date.valueOf("2025-04-01"), toDate.invoke(null, "2025-04-01T00:00:00+05:00"));
+    assertEquals(Date.valueOf("2025-04-01"), toDate.invoke(null, "2025-04-01T00:00:00.000+05:00"));
+    assertEquals(Date.valueOf("2025-04-01"), toDate.invoke(null, "2025-04-01T00:00:00.000Z"));
+  }
+
+  @Test
+  public void testToTimeIsoAndJdbc() throws Exception {
+    Method toTime = org.apache.calcite.avatica.AvaticaSite.class.getDeclaredMethod("toTime",
+        Object.class);
+    toTime.setAccessible(true);
+
+    assertEquals(Time.valueOf("21:39:50"), toTime.invoke(null, "21:39:50"));
+    assertEquals(Time.valueOf("21:39:50"), toTime.invoke(null, "21:39:50Z"));
+    assertEquals(Time.valueOf("21:39:50"), toTime.invoke(null, "21:39:50+05:00"));
+  }
+
+  @Test
+  public void testToTimestampIsoAndJdbc() throws Exception {
+    Method toTimestamp = org.apache.calcite.avatica.AvaticaSite.class.getDeclaredMethod(
+        "toTimestamp", Object.class);
+    toTimestamp.setAccessible(true);
+
+    assertEquals(
+        Timestamp.valueOf("2025-08-14 15:53:00.0"),
+        toTimestamp.invoke(null, "2025-08-14 15:53:00.0")
+    );
+    assertEquals(
+        Timestamp.valueOf("2025-08-14 15:53:00.0"),
+        toTimestamp.invoke(null, "2025-08-14T15:53:00")
+    );
+    assertEquals(
+        Timestamp.from(Instant.parse("2025-08-14T15:53:00.000Z")),
+        toTimestamp.invoke(null, "2025-08-14T15:53:00.000Z")
+    );
+  }
+}