如何获取可指定各时区瞬时时间的datetime对象？如何创建适配时区显示等效时间的固定时区datetime对象？

Hey there! Let's break down your two timezone-related datetime questions—this is such a common need when building global applications, so I’ll walk you through the best practices and code examples.

The key here is to work with timezone-aware datetime objects (not naive ones that lack timezone info) using standard timezone identifiers from the IANA Time Zone Database to avoid issues like daylight saving time shifts.

Starting with Python 3.9+, the built-in zoneinfo module is the recommended tool (no external dependencies needed). Here’s how to use it:

from zoneinfo import ZoneInfo
from datetime import datetime

# Option 1: Get current UTC time first, then convert to your target timezone
utc_now = datetime.now(ZoneInfo("UTC"))
sydney_now = utc_now.astimezone(ZoneInfo("Australia/Sydney"))

# Option 2: Directly create the current time for a specific timezone
berlin_now = datetime.now(ZoneInfo("Europe/Berlin"))

# Print results to verify
print(f"UTC current time: {utc_now}")
print(f"Sydney current time: {sydney_now}")
print(f"Berlin current time: {berlin_now}")

For Python versions before 3.9, you can use the pytz library (install it via pip install pytz):

import pytz
from datetime import datetime

utc_now = datetime.now(pytz.utc)
mexico_city_now = utc_now.astimezone(pytz.timezone("America/Mexico_City"))

Important notes:

• Always use IANA timezone names like Asia/Tokyo or Africa/Johannesburg instead of raw offsets (like UTC+6). This ensures your code handles daylight saving time and historical timezone changes automatically.
• Naive datetime objects (without tzinfo) don’t represent a specific instantaneous time—always convert them to timezone-aware objects first.

Your example describes exactly how timezone conversion works: the underlying instantaneous time never changes—you’re just displaying it in different timezone contexts. Here’s how to implement this:

First, define a single timezone-aware datetime (this represents your fixed instantaneous time). Then convert it to any target timezone to get the equivalent local time for that region.

Using zoneinfo (Python 3.9+):

from zoneinfo import ZoneInfo
from datetime import datetime

# Step 1: Create your base instantaneous time (using UTC as the reference here)
# This represents the exact same moment across all timezones
base_instant = datetime(2024, 5, 15, 0, 0, 0, tzinfo=ZoneInfo("UTC"))

# Step 2: Convert to UTC+6 timezone (e.g., Asia/Dhaka uses UTC+6 as standard offset)
utc_plus_6_time = base_instant.astimezone(ZoneInfo("Asia/Dhaka"))

# Step 3: Convert back to UTC (UTC+0)
utc_time = base_instant.astimezone(ZoneInfo("UTC"))

# Print the formatted times to match your example
print(f"User in UTC+6 sees: {utc_plus_6_time.strftime('%H:%M:%S')}")  # Output: 06:00:00
print(f"User in UTC+0 sees: {utc_time.strftime('%H:%M:%S')}")        # Output: 00:00:00

With pytz (for older Python versions):

import pytz
from datetime import datetime

base_instant = datetime(2024, 5, 15, 0, 0, 0, tzinfo=pytz.utc)
utc_plus_6_time = base_instant.astimezone(pytz.timezone("Asia/Dhaka"))
utc_time = base_instant.astimezone(pytz.utc)

print(f"User in UTC+6 sees: {utc_plus_6_time.strftime('%H:%M:%S')}")
print(f"User in UTC+0 sees: {utc_time.strftime('%H:%M:%S')}")

The core idea here is:

• The base_instant is a fixed point in time (it doesn’t change).
• Calling astimezone() with a different timezone returns a new datetime object that represents the same instantaneous time, but displayed in the target timezone’s local time.

内容的提问来源于stack exchange，提问作者Mohamed Ali Martins Agoussine