diff --git a/src/google/adk/sessions/database_session_service.py b/src/google/adk/sessions/database_session_service.py
index 2ccd60083..ec09b1473 100644
--- a/src/google/adk/sessions/database_session_service.py
+++ b/src/google/adk/sessions/database_session_service.py
@@ -15,6 +15,7 @@
 
 import copy
 from datetime import datetime
+from datetime import timezone
 import json
 import logging
 from typing import Any
@@ -27,6 +28,7 @@
 from sqlalchemy import Dialect
 from sqlalchemy import ForeignKeyConstraint
 from sqlalchemy import func
+from sqlalchemy import inspect
 from sqlalchemy import Text
 from sqlalchemy.dialects import mysql
 from sqlalchemy.dialects import postgresql
@@ -131,9 +133,11 @@ class StorageSession(Base):
       MutableDict.as_mutable(DynamicJSON), default={}
   )
 
-  create_time: Mapped[DateTime] = mapped_column(DateTime(), default=func.now())
+  create_time: Mapped[DateTime] = mapped_column(
+      DateTime(timezone=True), default=func.now()
+  )
   update_time: Mapped[DateTime] = mapped_column(
-      DateTime(), default=func.now(), onupdate=func.now()
+      DateTime(timezone=True), default=func.now(), onupdate=func.now()
   )
 
   storage_events: Mapped[list["StorageEvent"]] = relationship(
@@ -144,6 +148,19 @@ class StorageSession(Base):
   def __repr__(self):
     return f"<StorageSession(id={self.id}, update_time={self.update_time})>"
 
+  @property
+  def _dialect_name(self) -> str:
+    session = inspect(self).session
+    return session.bind.dialect.name if session else ""
+
+  @property
+  def create_timestamp_utc(self) -> datetime:
+    return _convert_datetime_to_utc(self.create_time, self._dialect_name)
+
+  @property
+  def update_timestamp_utc(self) -> datetime:
+    return _convert_datetime_to_utc(self.update_time, self._dialect_name)
+
 
 class StorageEvent(Base):
   """Represents an event stored in the database."""
@@ -278,7 +295,7 @@ class StorageAppState(Base):
       MutableDict.as_mutable(DynamicJSON), default={}
   )
   update_time: Mapped[DateTime] = mapped_column(
-      DateTime(), default=func.now(), onupdate=func.now()
+      DateTime(timezone=True), default=func.now(), onupdate=func.now()
   )
 
 
@@ -297,7 +314,7 @@ class StorageUserState(Base):
       MutableDict.as_mutable(DynamicJSON), default={}
   )
   update_time: Mapped[DateTime] = mapped_column(
-      DateTime(), default=func.now(), onupdate=func.now()
+      DateTime(timezone=True), default=func.now(), onupdate=func.now()
   )
 
 
@@ -412,7 +429,7 @@ async def create_session(
           user_id=str(storage_session.user_id),
           id=str(storage_session.id),
           state=merged_state,
-          last_update_time=storage_session.update_time.timestamp(),
+          last_update_time=storage_session.update_timestamp_utc,
       )
       return session
 
@@ -473,7 +490,7 @@ async def get_session(
           user_id=user_id,
           id=session_id,
           state=merged_state,
-          last_update_time=storage_session.update_time.timestamp(),
+          last_update_time=storage_session.update_timestamp_utc,
       )
       session.events = [e.to_event() for e in reversed(storage_events)]
     return session
@@ -496,7 +513,7 @@ async def list_sessions(
             user_id=user_id,
             id=storage_session.id,
             state={},
-            last_update_time=storage_session.update_time.timestamp(),
+            last_update_time=storage_session.update_timestamp_utc,
         )
         sessions.append(session)
       return ListSessionsResponse(sessions=sessions)
@@ -529,13 +546,13 @@ async def append_event(self, session: Session, event: Event) -> Event:
           StorageSession, (session.app_name, session.user_id, session.id)
       )
 
-      if storage_session.update_time.timestamp() > session.last_update_time:
+      if storage_session.update_timestamp_utc > session.last_update_time:
         raise ValueError(
             "The last_update_time provided in the session object"
             f" {datetime.fromtimestamp(session.last_update_time):'%Y-%m-%d %H:%M:%S'} is"
             " earlier than the update_time in the storage_session"
-            f" {storage_session.update_time:'%Y-%m-%d %H:%M:%S'}. Please check"
-            " if it is a stale session."
+            f" {datetime.fromtimestamp(storage_session.update_timestamp_utc):'%Y-%m-%d %H:%M:%S'}."
+            " Please check if it is a stale session."
         )
 
       # Fetch states from storage
@@ -577,7 +594,7 @@ async def append_event(self, session: Session, event: Event) -> Event:
       session_factory.refresh(storage_session)
 
       # Update timestamp with commit time
-      session.last_update_time = storage_session.update_time.timestamp()
+      session.last_update_time = storage_session.update_timestamp_utc
 
     # Also update the in-memory session
     await super().append_event(session=session, event=event)
@@ -607,3 +624,15 @@ def _merge_state(app_state, user_state, session_state):
   for key in user_state.keys():
     merged_state[State.USER_PREFIX + key] = user_state[key]
   return merged_state
+
+
+def _convert_datetime_to_utc(dt: DateTime, dialect_name: str) -> datetime:
+  if dialect_name == "sqlite":
+    # SQLite does not support timezone. SQLAlchemy returns a naive datetime
+    # object without timezone information. We need to convert it to UTC
+    # manually.
+    return dt.replace(tzinfo=timezone.utc).timestamp()
+  else:
+    # For other dialects, SQLAlchemy returns a datetime object with timezone
+    # information. We can safely convert it to UTC.
+    return dt.astimezone(timezone.utc).timestamp()