Demo Python logging with time zone information for field `asctime`

timezone_logging_demo.py

#! /usr/bin/env python3
# Copyright (c) Sebastian Pipping <[email protected]>
#
# Licensed under Zero-Clause BSD
# SPDX-License-Identifier: 0BSD

import datetime
import logging


class CustomFormatter(logging.Formatter):
    def formatTime(self, record, datefmt=None):
        local_time_zone = datetime.datetime.now().astimezone().tzinfo
        dt = datetime.datetime.fromtimestamp(record.created, tz=local_time_zone)
        return dt.isoformat(sep=" ", timespec="milliseconds")


format_ = "[%(asctime)s][%(levelname)s] %(message)s"

logging.basicConfig(format=format_)

logging.warning("First warning, no time zone")

# Now install customer formatter class
formatter = CustomFormatter(fmt=format_)
for handler in logging.root.handlers:
    handler.setFormatter(formatter)

logging.warning("Second warning, with time zone")

Output:

# python3 timezone_logging_demo.py 
[2025-05-05 17:15:08,341][WARNING] First warning, no time zone
[2025-05-05 17:15:08.341+02:00][WARNING] Second warning, with time zone