refactor: move all datetime.now() calls to UTC

Updated all instances of datetime.now() to use timezone.utc for
consistency in handling time across different systems. This ensures that
timestamps are always in Coordinated Universal Time (UTC), avoiding
issues with time zone discrepancies and promoting uniformity in
time-related data.

Signed-off-by: Sébastien Han <seb@redhat.com>

llama_stack/providers/inline/post_training/torchtune/post_training.py

@@ -3,7 +3,7 @@
 #
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Any, Dict, Optional
 
 from llama_stack.apis.datasetio import DatasetIO
@@ -64,7 +64,7 @@ class TorchtunePostTrainingImpl:
         job_status_response = PostTrainingJobStatusResponse(
             job_uuid=job_uuid,
             status=JobStatus.scheduled,
-            scheduled_at=datetime.now(),
+            scheduled_at=datetime.now(timezone.utc),
         )
         self.jobs[job_uuid] = job_status_response
 
@@ -84,7 +84,7 @@ class TorchtunePostTrainingImpl:
                 )
 
                 job_status_response.status = JobStatus.in_progress
-                job_status_response.started_at = datetime.now()
+                job_status_response.started_at = datetime.now(timezone.utc)
 
                 await recipe.setup()
                 resources_allocated, checkpoints = await recipe.train()
@@ -93,7 +93,7 @@ class TorchtunePostTrainingImpl:
                 job_status_response.resources_allocated = resources_allocated
                 job_status_response.checkpoints = checkpoints
                 job_status_response.status = JobStatus.completed
-                job_status_response.completed_at = datetime.now()
+                job_status_response.completed_at = datetime.now(timezone.utc)
 
             except Exception:
                 job_status_response.status = JobStatus.failed

llama_stack/providers/inline/post_training/torchtune/recipes/lora_finetuning_single_device.py

@@ -8,7 +8,7 @@ import gc
 import logging
 import os
 import time
-from datetime import datetime
+from datetime import datetime, timezone
 from functools import partial
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple
@@ -532,7 +532,7 @@ class LoraFinetuningSingleDevice:
             checkpoint_path = await self.save_checkpoint(epoch=curr_epoch)
             checkpoint = Checkpoint(
                 identifier=f"{self.model_id}-sft-{curr_epoch}",
-                created_at=datetime.now(),
+                created_at=datetime.now(timezone.utc),
                 epoch=curr_epoch,
                 post_training_job_id=self.job_uuid,
                 path=checkpoint_path,