fix: replace datetime.UTC with timezone.utc for Python 3.12+ compatibility

apps/blockchain-node/create_genesis.py

@@ -8,7 +8,7 @@ sys.path.insert(0, 'src')
 
 from aitbc_chain.database import session_scope, init_db
 from aitbc_chain.models import Block
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 import hashlib
 
 def compute_block_hash(height: int, parent_hash: str, timestamp: datetime) -> str:
@@ -31,7 +31,7 @@ def create_genesis():
             return
         
         # Create genesis block
-        timestamp = datetime.now(datetime.UTC)
+        timestamp = datetime.now(timezone.utc)
         genesis_hash = compute_block_hash(0, "0x00", timestamp)
         genesis = Block(
             height=0,

apps/blockchain-node/fix_accounts.py

@@ -1,11 +1,11 @@
 from aitbc_chain.database import session_scope, init_db
 from aitbc_chain.models import Account
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 
 def fix():
     init_db()
     with session_scope() as session:
-        acc = Account(chain_id="ait-mainnet", address="aitbc1genesis", balance=10000000, nonce=0, updated_at=datetime.now(datetime.UTC), account_type="regular", metadata="{}")
+        acc = Account(chain_id="ait-mainnet", address="aitbc1genesis", balance=10000000, nonce=0, updated_at=datetime.now(timezone.utc), account_type="regular", metadata="{}")
         session.merge(acc)
         session.commit()
         print("Added aitbc1genesis to mainnet")

apps/blockchain-node/scripts/unified_genesis.py

@@ -18,7 +18,7 @@ import base64
 import os
 import sys
 from pathlib import Path
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 from typing import Dict, List, Any, Optional
 
 from cryptography.hazmat.primitives.asymmetric import ed25519
@@ -233,7 +233,7 @@ def initialize_genesis_database(genesis_block: Dict, allocations: List[Dict], db
                     alloc["address"],
                     alloc["balance"],
                     alloc["nonce"],
-                    datetime.now(datetime.UTC).isoformat()
+                    datetime.now(timezone.utc).isoformat()
                 )
             )
         

apps/blockchain-node/src/aitbc_chain/contracts/agent_wallet_security.py

@@ -8,7 +8,7 @@ of agent compromise.
 
 from typing import Dict, List, Optional, Tuple
 from dataclasses import dataclass
-from datetime import datetime, UTC, timedelta
+from datetime import datetime, timezone, timedelta
 import json
 from eth_account import Account
 from eth_utils import to_checksum_address
@@ -37,7 +37,7 @@ class AgentSecurityProfile:
     
     def __post_init__(self):
         if self.created_at is None:
-            self.created_at = datetime.now(datetime.UTC)
+            self.created_at = datetime.now(timezone.utc)
 
 
 class AgentWalletSecurity:
@@ -423,7 +423,7 @@ class AgentWalletSecurity:
     def _log_security_event(self, **kwargs):
         """Log a security event"""
         event = {
-            "timestamp": datetime.now(datetime.UTC).isoformat(),
+            "timestamp": datetime.now(timezone.utc).isoformat(),
             **kwargs
         }
         self.security_events.append(event)
@@ -469,7 +469,7 @@ class AgentWalletSecurity:
             return {
                 "status": "disabled",
                 "agent_address": agent_address,
-                "disabled_at": datetime.now(datetime.UTC).isoformat(),
+                "disabled_at": datetime.now(timezone.utc).isoformat(),
                 "guardian": guardian_address
             }
             
@@ -527,7 +527,7 @@ def generate_security_report() -> Dict:
     recent_events = agent_wallet_security.get_security_events(limit=20)
     
     return {
-        "generated_at": datetime.now(datetime.UTC).isoformat(),
+        "generated_at": datetime.now(timezone.utc).isoformat(),
         "summary": {
             "total_protected_agents": total_agents,
             "active_agents": active_agents,
@@ -580,5 +580,5 @@ def detect_suspicious_activity(agent_address: str, hours: int = 24) -> Dict:
         "suspicious_activity": len(suspicious_patterns) > 0,
         "suspicious_patterns": suspicious_patterns,
         "analysis_period_hours": hours,
-        "analyzed_at": datetime.now(datetime.UTC).isoformat()
+        "analyzed_at": datetime.now(timezone.utc).isoformat()
     }

apps/blockchain-node/src/aitbc_chain/contracts/guardian_contract.py

@@ -12,7 +12,7 @@ wallets from unlimited spending in case of compromise. It provides:
 
 from typing import Dict, List, Optional, Tuple
 from dataclasses import dataclass
-from datetime import datetime, UTC, timedelta
+from datetime import datetime, timezone, timedelta
 import json
 import os
 import sqlite3
@@ -248,7 +248,7 @@ class GuardianContract:
     def _get_spent_in_period(self, period: str, timestamp: datetime = None) -> int:
         """Calculate total spent in given period"""
         if timestamp is None:
-            timestamp = datetime.now(datetime.UTC)
+            timestamp = datetime.now(timezone.utc)
             
         period_key = self._get_period_key(timestamp, period)
         
@@ -265,7 +265,7 @@ class GuardianContract:
     def _check_spending_limits(self, amount: int, timestamp: datetime = None) -> Tuple[bool, str]:
         """Check if amount exceeds spending limits"""
         if timestamp is None:
-            timestamp = datetime.now(datetime.UTC)
+            timestamp = datetime.now(timezone.utc)
             
         # Check per-transaction limit
         if amount > self.config.limits.per_transaction:
@@ -350,7 +350,7 @@ class GuardianContract:
             "to": to_address,
             "amount": amount,
             "data": data,
-            "timestamp": datetime.now(datetime.UTC).isoformat(),
+            "timestamp": datetime.now(timezone.utc).isoformat(),
             "nonce": self.nonce,
             "status": "pending"
         }
@@ -360,7 +360,7 @@ class GuardianContract:
         
         # Check if time lock is required
         if self._requires_time_lock(amount):
-            unlock_time = datetime.now(datetime.UTC) + timedelta(hours=self.config.time_lock.delay_hours)
+            unlock_time = datetime.now(timezone.utc) + timedelta(hours=self.config.time_lock.delay_hours)
             operation["unlock_time"] = unlock_time.isoformat()
             operation["status"] = "time_locked"
             
@@ -406,7 +406,7 @@ class GuardianContract:
         # Check if operation is time locked
         if operation["status"] == "time_locked":
             unlock_time = datetime.fromisoformat(operation["unlock_time"])
-            if datetime.now(datetime.UTC) < unlock_time:
+            if datetime.now(timezone.utc) < unlock_time:
                 return {
                     "status": "error",
                     "reason": f"Operation locked until {unlock_time.isoformat()}"
@@ -432,7 +432,7 @@ class GuardianContract:
             "amount": operation["amount"],
             "data": operation.get("data", ""),
             "timestamp": operation["timestamp"],
-            "executed_at": datetime.now(datetime.UTC).isoformat(),
+            "executed_at": datetime.now(timezone.utc).isoformat(),
             "status": "completed",
             "nonce": operation["nonce"]
         }
@@ -479,7 +479,7 @@ class GuardianContract:
         
         return {
             "status": "paused",
-            "paused_at": datetime.now(datetime.UTC).isoformat(),
+            "paused_at": datetime.now(timezone.utc).isoformat(),
             "guardian": guardian_address,
             "message": "Emergency pause activated - all operations halted"
         }
@@ -513,7 +513,7 @@ class GuardianContract:
         
         return {
             "status": "unpaused",
-            "unpaused_at": datetime.now(datetime.UTC).isoformat(),
+            "unpaused_at": datetime.now(timezone.utc).isoformat(),
             "message": "Emergency pause lifted - operations resumed"
         }
     
@@ -541,13 +541,13 @@ class GuardianContract:
             "status": "updated",
             "old_limits": old_limits,
             "new_limits": new_limits,
-            "updated_at": datetime.now(datetime.UTC).isoformat(),
+            "updated_at": datetime.now(timezone.utc).isoformat(),
             "guardian": guardian_address
         }
     
     def get_spending_status(self) -> Dict:
         """Get current spending status and limits"""
-        now = datetime.now(datetime.UTC)
+        now = datetime.now(timezone.utc)
         
         return {
             "agent_address": self.agent_address,

apps/blockchain-node/src/aitbc_chain/contracts/persistent_spending_tracker.py

@@ -5,7 +5,7 @@ Fixes the critical vulnerability where spending limits were lost on restart
 
 from typing import Dict, List, Optional, Tuple
 from dataclasses import dataclass
-from datetime import datetime, UTC, timedelta
+from datetime import datetime, timezone, timedelta
 from sqlalchemy import create_engine, Column, String, Integer, Float, DateTime, Index
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import sessionmaker, Session
@@ -25,7 +25,7 @@ class SpendingRecord(Base):
     period_key = Column(String, index=True)
     amount = Column(Float)
     transaction_hash = Column(String)
-    timestamp = Column(DateTime, default=datetime.now(datetime.UTC))
+    timestamp = Column(DateTime, default=datetime.now(timezone.utc))
     
     # Composite indexes for performance
     __table_args__ = (
@@ -45,7 +45,7 @@ class SpendingLimit(Base):
     per_week = Column(Float)
     time_lock_threshold = Column(Float)
     time_lock_delay_hours = Column(Integer)
-    updated_at = Column(DateTime, default=datetime.now(datetime.UTC))
+    updated_at = Column(DateTime, default=datetime.now(timezone.utc))
     updated_by = Column(String)  # Guardian who updated
 
 
@@ -57,7 +57,7 @@ class GuardianAuthorization(Base):
     agent_address = Column(String, index=True)
     guardian_address = Column(String, index=True)
     is_active = Column(Boolean, default=True)
-    added_at = Column(DateTime, default=datetime.now(datetime.UTC))
+    added_at = Column(DateTime, default=datetime.now(timezone.utc))
     added_by = Column(String)
 
 
@@ -112,7 +112,7 @@ class PersistentSpendingTracker:
             Total amount spent in period
         """
         if timestamp is None:
-            timestamp = datetime.now(datetime.UTC)
+            timestamp = datetime.now(timezone.utc)
         
         period_key = self._get_period_key(timestamp, period)
         agent_address = to_checksum_address(agent_address)
@@ -140,7 +140,7 @@ class PersistentSpendingTracker:
             True if recorded successfully
         """
         if timestamp is None:
-            timestamp = datetime.now(datetime.UTC)
+            timestamp = datetime.now(timezone.utc)
         
         agent_address = to_checksum_address(agent_address)
         
@@ -184,7 +184,7 @@ class PersistentSpendingTracker:
             Spending check result
         """
         if timestamp is None:
-            timestamp = datetime.now(datetime.UTC)
+            timestamp = datetime.now(timezone.utc)
         
         agent_address = to_checksum_address(agent_address)
         
@@ -312,7 +312,7 @@ class PersistentSpendingTracker:
                     limits.per_week = new_limits.get("per_week", limits.per_week)
                     limits.time_lock_threshold = new_limits.get("time_lock_threshold", limits.time_lock_threshold)
                     limits.time_lock_delay_hours = new_limits.get("time_lock_delay_hours", limits.time_lock_delay_hours)
-                    limits.updated_at = datetime.now(datetime.UTC)
+                    limits.updated_at = datetime.now(timezone.utc)
                     limits.updated_by = guardian_address
                 else:
                     limits = SpendingLimit(
@@ -323,7 +323,7 @@ class PersistentSpendingTracker:
                         per_week=new_limits.get("per_week", 100000.0),
                         time_lock_threshold=new_limits.get("time_lock_threshold", 5000.0),
                         time_lock_delay_hours=new_limits.get("time_lock_delay_hours", 24),
-                        updated_at=datetime.now(datetime.UTC),
+                        updated_at=datetime.now(timezone.utc),
                         updated_by=guardian_address
                     )
                     session.add(limits)
@@ -361,7 +361,7 @@ class PersistentSpendingTracker:
                 
                 if existing:
                     existing.is_active = True
-                    existing.added_at = datetime.now(datetime.UTC)
+                    existing.added_at = datetime.now(timezone.utc)
                     existing.added_by = added_by
                 else:
                     auth = GuardianAuthorization(
@@ -369,7 +369,7 @@ class PersistentSpendingTracker:
                         agent_address=agent_address,
                         guardian_address=guardian_address,
                         is_active=True,
-                        added_at=datetime.now(datetime.UTC),
+                        added_at=datetime.now(timezone.utc),
                         added_by=added_by
                     )
                     session.add(auth)
@@ -415,7 +415,7 @@ class PersistentSpendingTracker:
             Spending summary
         """
         agent_address = to_checksum_address(agent_address)
-        now = datetime.now(datetime.UTC)
+        now = datetime.now(timezone.utc)
         
         # Get current spending
         current_spent = {

apps/blockchain-node/src/aitbc_chain/cross_chain.py

@@ -1,7 +1,7 @@
 """Cross-chain synchronization for testing multi-chain scenarios."""
 
 import asyncio
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 from typing import Any, Dict, List
 
 

apps/blockchain-node/src/aitbc_chain/rpc/router.py

@@ -4,7 +4,7 @@ import asyncio
 import json
 import time
 from typing import Any, Dict, Optional, List
-from datetime import datetime, UTC, timedelta
+from datetime import datetime, timezone, timedelta
 
 from fastapi import APIRouter, HTTPException, status
 from pydantic import BaseModel, Field, model_validator
@@ -478,12 +478,12 @@ async def submit_marketplace_transaction(tx_data: Dict[str, Any]) -> Dict[str, A
                 sender=sender_addr,
                 recipient=recipient_addr,
                 payload=tx_data.get("payload", {}),
-                created_at=datetime.now(datetime.UTC),
+                created_at=datetime.now(timezone.utc),
                 nonce=tx_nonce,
                 value=amount,
                 fee=fee,
                 status="pending",
-                timestamp=datetime.now(datetime.UTC).isoformat()
+                timestamp=datetime.now(timezone.utc).isoformat()
             )
             session.add(transaction)
             
@@ -798,9 +798,9 @@ async def import_block(block_data: dict) -> Dict[str, Any]:
                 try:
                     timestamp = datetime.fromisoformat(timestamp.replace('Z', '+00:00'))
                 except ValueError:
-                    timestamp = datetime.now(datetime.UTC)
+                    timestamp = datetime.now(timezone.utc)
             elif timestamp is None:
-                timestamp = datetime.now(datetime.UTC)
+                timestamp = datetime.now(timezone.utc)
 
             with session_scope(chain_id) as session:
                 # Check for hash conflicts across chains
@@ -1046,7 +1046,7 @@ async def import_chain(import_data: dict) -> Dict[str, Any]:
                  _logger.info(f"Importing {len(unique_blocks)} unique blocks (filtered from {len(blocks)} total)")
 
                  for block_data in unique_blocks:
-                     block_timestamp = _parse_datetime_value(block_data.get("timestamp"), "block timestamp") or datetime.now(datetime.UTC)
+                     block_timestamp = _parse_datetime_value(block_data.get("timestamp"), "block timestamp") or datetime.now(timezone.utc)
                      block = Block(
                          chain_id=chain_id,
                          height=block_data["height"],

apps/blockchain-node/src/aitbc_chain/state/state_transition.py

@@ -11,7 +11,7 @@ from typing import Dict, List, Optional, Tuple
 
 from sqlmodel import Session, select
 from sqlalchemy import select, text
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 
 from ..models import Account, Transaction, Receipt
 from ..logger import get_logger
@@ -242,7 +242,7 @@ class StateTransition:
                 
                 # Update receipt status
                 receipt.status = "claimed"
-                receipt.claimed_at = datetime.now(datetime.UTC)
+                receipt.claimed_at = datetime.now(timezone.utc)
                 receipt.claimed_by = sender_addr
                 
                 logger.info(

apps/blockchain-node/src/aitbc_chain/sync.py

@@ -8,7 +8,7 @@ import hmac
 import json
 import time
 from dataclasses import dataclass
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 from typing import Any, Dict, List, Optional, Tuple
 
 import httpx
@@ -508,9 +508,9 @@ class ChainSync:
         block_hash = block_data["hash"]
         timestamp_str = block_data.get("timestamp", "")
         try:
-            timestamp = datetime.fromisoformat(timestamp_str) if timestamp_str else datetime.now(datetime.UTC)
+            timestamp = datetime.fromisoformat(timestamp_str) if timestamp_str else datetime.now(timezone.utc)
         except (ValueError, TypeError):
-            timestamp = datetime.now(datetime.UTC)
+            timestamp = datetime.now(timezone.utc)
 
         tx_count = block_data.get("tx_count", 0)
         if transactions:

apps/blockchain-node/tests/test_consensus.py

@@ -5,7 +5,7 @@ from __future__ import annotations
 import sys
 import asyncio
 import pytest
-from datetime import datetime, UTC, timedelta
+from datetime import datetime, timezone, timedelta
 from unittest.mock import AsyncMock, Mock, patch
 from typing import Generator
 
@@ -192,7 +192,7 @@ class TestPoAProposer:
             hash="0xparent",
             parent_hash="0x00",
             proposer="previous-proposer",
-            timestamp=datetime.now(datetime.UTC),
+            timestamp=datetime.now(timezone.utc),
             tx_count=0,
         )
         test_db.add(parent)
@@ -231,16 +231,16 @@ class TestPoAProposer:
             hash="0xhead",
             parent_hash="0x00",
             proposer="test-proposer",
-            timestamp=datetime.now(datetime.UTC),
+            timestamp=datetime.now(timezone.utc),
             tx_count=0,
         )
         test_db.add(head)
         test_db.commit()
         
         # Should wait for the configured interval
-        start_time = datetime.now(datetime.UTC)
+        start_time = datetime.now(timezone.utc)
         await proposer._wait_until_next_slot()
-        elapsed = (datetime.now(datetime.UTC) - start_time).total_seconds()
+        elapsed = (datetime.now(timezone.utc) - start_time).total_seconds()
         
         # Should wait at least some time (but less than full interval since block is recent)
         assert elapsed >= 0.1
@@ -255,7 +255,7 @@ class TestPoAProposer:
             hash="0xhead",
             parent_hash="0x00",
             proposer="test-proposer",
-            timestamp=datetime.now(datetime.UTC) - timedelta(seconds=10),
+            timestamp=datetime.now(timezone.utc) - timedelta(seconds=10),
             tx_count=0,
         )
         test_db.add(head)
@@ -263,9 +263,9 @@ class TestPoAProposer:
         
         # Set stop event and wait
         proposer._stop_event.set()
-        start_time = datetime.now(datetime.UTC)
+        start_time = datetime.now(timezone.utc)
         await proposer._wait_until_next_slot()
-        elapsed = (datetime.now(datetime.UTC) - start_time).total_seconds()
+        elapsed = (datetime.now(timezone.utc) - start_time).total_seconds()
         
         # Should return immediately due to stop event
         assert elapsed < 0.1
@@ -290,7 +290,7 @@ class TestPoAProposer:
         """Test block hash computation."""
         height = 1
         parent_hash = "0xparent"
-        timestamp = datetime.now(datetime.UTC)
+        timestamp = datetime.now(timezone.utc)
         processed_txs = []
         
         block_hash = proposer._compute_block_hash(height, parent_hash, timestamp, processed_txs)
@@ -303,7 +303,7 @@ class TestPoAProposer:
         """Test block hash computation with transactions."""
         height = 1
         parent_hash = "0xparent"
-        timestamp = datetime.now(datetime.UTC)
+        timestamp = datetime.now(timezone.utc)
         
         mock_tx = Mock()
         mock_tx.tx_hash = "0xtx"
@@ -324,7 +324,7 @@ class TestPoAProposer:
             hash="0xexisting",
             parent_hash="0x00",
             proposer="test-proposer",
-            timestamp=datetime.now(datetime.UTC),
+            timestamp=datetime.now(timezone.utc),
             tx_count=0,
         )
         test_db.add(block)

apps/blockchain-node/tests/test_guardian_contract.py

@@ -6,7 +6,7 @@ import sys
 import pytest
 import tempfile
 import shutil
-from datetime import datetime, UTC, timedelta
+from datetime import datetime, timezone, timedelta
 from pathlib import Path
 from unittest.mock import patch, Mock
 from typing import Generator
@@ -113,7 +113,7 @@ class TestGuardianContract:
     def test_spending_limit_check_hourly(self, guardian_contract: GuardianContract) -> None:
         """Test hourly spending limit."""
         # Add some spending history
-        base_time = datetime.now(datetime.UTC)
+        base_time = datetime.now(timezone.utc)
         guardian_contract.spending_history = [
             {
                 "operation_id": "op1",
@@ -139,7 +139,7 @@ class TestGuardianContract:
     def test_spending_limit_check_daily(self, guardian_contract: GuardianContract) -> None:
         """Test daily spending limit."""
         # Add spending history across the day
-        base_time = datetime.now(datetime.UTC)
+        base_time = datetime.now(timezone.utc)
         guardian_contract.spending_history = [
             {
                 "operation_id": "op1",
@@ -165,7 +165,7 @@ class TestGuardianContract:
     def test_spending_limit_check_weekly(self, guardian_contract: GuardianContract) -> None:
         """Test weekly spending limit."""
         # Add spending history across the week
-        base_time = datetime.now(datetime.UTC)
+        base_time = datetime.now(timezone.utc)
         guardian_contract.spending_history = [
             {
                 "operation_id": "op1",

apps/blockchain-node/tests/test_sync.py

@@ -4,7 +4,7 @@ import hashlib
 import time
 import sys
 import pytest
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 from contextlib import contextmanager
 from unittest.mock import AsyncMock, Mock
 
@@ -70,7 +70,7 @@ class TestProposerSignatureValidator:
 
     def test_valid_block(self):
         v = ProposerSignatureValidator()
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 1, "0x00", ts)
         ok, reason = v.validate_block_signature({
             "height": 1, "hash": bh, "parent_hash": "0x00",
@@ -83,7 +83,7 @@ class TestProposerSignatureValidator:
         v = ProposerSignatureValidator()
         ok, reason = v.validate_block_signature({
             "height": 1, "hash": "0x" + "a" * 64, "parent_hash": "0x00",
-            "timestamp": datetime.now(datetime.UTC).isoformat(),
+            "timestamp": datetime.now(timezone.utc).isoformat(),
         })
         assert ok is False
         assert "Missing proposer" in reason
@@ -92,7 +92,7 @@ class TestProposerSignatureValidator:
         v = ProposerSignatureValidator()
         ok, reason = v.validate_block_signature({
             "height": 1, "hash": "badhash", "parent_hash": "0x00",
-            "proposer": "node-a", "timestamp": datetime.now(datetime.UTC).isoformat(),
+            "proposer": "node-a", "timestamp": datetime.now(timezone.utc).isoformat(),
         })
         assert ok is False
         assert "Invalid block hash" in reason
@@ -101,14 +101,14 @@ class TestProposerSignatureValidator:
         v = ProposerSignatureValidator()
         ok, reason = v.validate_block_signature({
             "height": 1, "hash": "0xabc", "parent_hash": "0x00",
-            "proposer": "node-a", "timestamp": datetime.now(datetime.UTC).isoformat(),
+            "proposer": "node-a", "timestamp": datetime.now(timezone.utc).isoformat(),
         })
         assert ok is False
         assert "Invalid hash length" in reason
 
     def test_untrusted_proposer_rejected(self):
         v = ProposerSignatureValidator(trusted_proposers=["node-a", "node-b"])
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 1, "0x00", ts)
         ok, reason = v.validate_block_signature({
             "height": 1, "hash": bh, "parent_hash": "0x00",
@@ -119,7 +119,7 @@ class TestProposerSignatureValidator:
 
     def test_trusted_proposer_accepted(self):
         v = ProposerSignatureValidator(trusted_proposers=["node-a"])
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 1, "0x00", ts)
         ok, reason = v.validate_block_signature({
             "height": 1, "hash": bh, "parent_hash": "0x00",
@@ -149,7 +149,7 @@ class TestChainSyncAppend:
 
     def test_append_to_empty_chain(self, session_factory):
         sync = ChainSync(session_factory, chain_id="test", validate_signatures=False)
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 0, "0x00", ts)
         result = sync.import_block({
             "height": 0, "hash": bh, "parent_hash": "0x00",
@@ -316,7 +316,7 @@ class TestChainSyncSignatureValidation:
     def test_untrusted_proposer_rejected_on_import(self, session_factory):
         validator = ProposerSignatureValidator(trusted_proposers=["node-a"])
         sync = ChainSync(session_factory, chain_id="test", validator=validator, validate_signatures=True)
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 0, "0x00", ts)
         result = sync.import_block({
             "height": 0, "hash": bh, "parent_hash": "0x00",
@@ -328,7 +328,7 @@ class TestChainSyncSignatureValidation:
     def test_trusted_proposer_accepted_on_import(self, session_factory):
         validator = ProposerSignatureValidator(trusted_proposers=["node-a"])
         sync = ChainSync(session_factory, chain_id="test", validator=validator, validate_signatures=True)
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 0, "0x00", ts)
         result = sync.import_block({
             "height": 0, "hash": bh, "parent_hash": "0x00",
@@ -339,7 +339,7 @@ class TestChainSyncSignatureValidation:
     def test_validation_disabled(self, session_factory):
         validator = ProposerSignatureValidator(trusted_proposers=["node-a"])
         sync = ChainSync(session_factory, chain_id="test", validator=validator, validate_signatures=False)
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 0, "0x00", ts)
         result = sync.import_block({
             "height": 0, "hash": bh, "parent_hash": "0x00",
@@ -379,7 +379,7 @@ class TestSyncMetrics:
 
     def test_accepted_block_increments_metrics(self, session_factory):
         sync = ChainSync(session_factory, chain_id="test", validate_signatures=False)
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 0, "0x00", ts)
         sync.import_block({
             "height": 0, "hash": bh, "parent_hash": "0x00",
@@ -392,7 +392,7 @@ class TestSyncMetrics:
     def test_rejected_block_increments_metrics(self, session_factory):
         validator = ProposerSignatureValidator(trusted_proposers=["node-a"])
         sync = ChainSync(session_factory, chain_id="test", validator=validator, validate_signatures=True)
-        ts = datetime.now(datetime.UTC)
+        ts = datetime.now(timezone.utc)
         bh = _make_block_hash("test", 0, "0x00", ts)
         sync.import_block({
             "height": 0, "hash": bh, "parent_hash": "0x00",