Python datetime Guide: Dates, Times, Time Zones & Examples

1. Introduction

• “I want to get the current date and time, but which function should I use?”
• “I don’t know how to handle time zones!”
• “How do I perform date calculations?”

2. datetime Module? Understand the Basic Concepts

2.1 Overview of the datetime module

2.2 How to import the datetime module

import datetime

# Get the current date and time
now = datetime.datetime.now()
print(now)

from datetime import datetime

# Get the current date and time
now = datetime.now()
print(now)

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3. How to get the current time and today’s date in Python (difference between now and today)

3.1 How to get the current date and time

from datetime import datetime

now = datetime.now()
print("Current date and time:", now)

Current date and time: 2025-02-01 12:34:56.789012

3.2 How to get today’s date

from datetime import date

today = date.today()
print("Today's date:", today)

Today's date: 2025-02-01

3.3 Difference between now() and today()

4. Date and Time Format Conversion (String ⇔ datetime)

4.1 Converting a datetime object to a string (strftime)

from datetime import datetime

now = datetime.now()
formatted_date = now.strftime("%Y-%m-%d %H:%M:%S")
print("Formatted date:", formatted_date)

Formatted date: 2025-02-01 12:34:56

4.2 Converting a string to a datetime object (strptime)

from datetime import datetime

date_str = "2025-02-01 12:34:56"
dt = datetime.strptime(date_str, "%Y-%m-%d %H:%M:%S")
print("Converted datetime object:", dt)

Converted datetime object: 2025-02-01 12:34:56

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5. How to add and subtract dates in Python (using timedelta)

5.1 Basics of the timedelta class

from datetime import datetime, timedelta

# Get the current date and time
now = datetime.now()

# Get the date 7 days from now
future_date = now + timedelta(days=7)
print("Date 7 days from now:", future_date)

# Get the date 3 days ago
past_date = now - timedelta(days=3)
print("Date 3 days ago:", past_date)

5.2 Adding and subtracting in time units

from datetime import datetime, timedelta

now = datetime.now()

# Time one hour later
one_hour_later = now + timedelta(hours=1)
print("Time one hour later:", one_hour_later)

# Time 30 minutes ago
thirty_minutes_ago = now - timedelta(minutes=30)
print("Time 30 minutes ago:", thirty_minutes_ago)

5.3 Calculating the difference between two dates

from datetime import datetime

# Define two dates
date1 = datetime(2025, 2, 10)
date2 = datetime(2025, 2, 1)

# Calculate the difference
difference = date1 - date2
print("Date difference:", difference)
print("Days difference:", difference.days, "days")

6. Handling Dates and Times with Time Zone Awareness (Differences between pytz and zoneinfo)

6.1 pytz Setting Time Zones

from datetime import datetime
import pytz

# Specify the time zone
japan_tz = pytz.timezone('Asia/Tokyo')

# Get the current UTC time
utc_now = datetime.utcnow()

# Convert to JST (Japan Standard Time)
jst_now = utc_now.replace(tzinfo=pytz.utc).astimezone(japan_tz)
print("Japan Time (JST):", jst_now)

6.2 zoneinfo (Python 3.9 and later) Setting Time Zones

from datetime import datetime
from zoneinfo import ZoneInfo

# Get the current time in JST (Japan Standard Time)
jst_now = datetime.now(ZoneInfo("Asia/Tokyo"))
print("Current JST time:", jst_now)

7. Errors and Their Solutions

7.1 AttributeError: type object 'datetime.datetime' has no attribute 'timedelta'

from datetime import datetime

# Trying to use timedelta but error
now = datetime.now()
new_date = now + datetime.timedelta(days=7)

from datetime import datetime, timedelta

now = datetime.now()
new_date = now + timedelta(days=7)
print(new_date)

7.2 TypeError: can't subtract offset-naive and offset-aware datetimes

from datetime import datetime
import pytz

dt_naive = datetime(2025, 2, 1, 12, 0)
dt_aware = datetime(2025, 2, 1, 12, 0, tzinfo=pytz.utc)

diff = dt_aware - dt_naive  # error occurs

dt_aware = dt_naive.replace(tzinfo=pytz.utc)

8. Practical Examples

8.1 How to Generate a Date Range

from datetime import datetime, timedelta

start_date = datetime(2025, 2, 1)
end_date = datetime(2025, 2, 7)

date_list = [start_date + timedelta(days=i) for i in range((end_date - start_date).days + 1)]

for date in date_list:
    print(date.strftime("%Y-%m-%d"))

8.2 Date Calculations Considering Business Days (Weekdays)

import pandas as pd

business_days = pd.bdate_range(start="2025-02-01", end="2025-02-10")

for day in business_days:
    print(day.date())

8.3 Converting UNIX Timestamps

from datetime import datetime

timestamp = 1735689600
dt = datetime.fromtimestamp(timestamp)
print("Converted datetime:", dt)

9. FAQ (Frequently Asked Questions)

9.1 Difference between datetime and time?

9.2 Difference between strftime and strptime?

from datetime import datetime

# datetime → string (strftime)
now = datetime(2025, 2, 1, 12, 0, 0)
formatted_str = now.strftime("%Y-%m-%d %H:%M:%S")
print("Convert to string:", formatted_str)

# string → datetime (strptime)
date_str = "2025-02-01 12:00:00"
parsed_date = datetime.strptime(date_str, "%Y-%m-%d %H:%M:%S")
print("Convert to datetime:", parsed_date)

9.3 How to convert a UNIX timestamp to datetime?

from datetime import datetime

timestamp = 1735689600
dt = datetime.fromtimestamp(timestamp)
print("Converted datetime:", dt)

10. Summary

10.1 Summary of Article Points

• datetime module is the standard library for handling dates and times in Python.
• Use datetime.now() to get the current date and time, and date.today() to get only the current date.
• Use strftime() to convert a <code to a string, and strptime() to convert a string to a datetime.
• Calculate the date one week later with timedelta(days=7).
• Use zoneinfo for Python 3.9 and later, and pytz for earlier versions.
• datetime objects can be compared using > < ==.

10.2 Official Documentation and References

• Python Official Documentation (datetime module)
• pytz Documentation
• zoneinfo (Python 3.9 and later)

10.3 Put Time Handling in Python into Practice

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