Working with Dates and Time in Python

Working with dates and time is a common task in most applications — whether it’s logging events, scheduling tasks, analyzing historical data, or interacting with user input. Python offers a powerful suite of modules and classes that make handling time and dates both simple and flexible.

In this chapter, we will explore:

• datetime module for basic and advanced operations
• time module for low-level manipulation
• calendar module for calendar-related tasks
• Formatting and parsing dates
• Timezone handling with pytz and zoneinfo
• Timedeltas and date arithmetic
• Real-world examples and best practices

1. Introduction to Date and Time in Python

Python’s built-in datetime, time, and calendar modules allow for precise and customizable date-time operations.

Why is it important?

• Stamping logs with the correct time
• Comparing or calculating date ranges
• Formatting date/time for user interfaces
• Scheduling or automation tasks

2. The datetime Module

This is the most commonly used module for working with both dates and times.

2.1 Importing:

import datetime

2.2 Getting Current Date and Time:

now = datetime.datetime.now()
print(now)

2.3 Components:

print("Year:", now.year)
print("Month:", now.month)
print("Day:", now.day)
print("Hour:", now.hour)
print("Minute:", now.minute)
print("Second:", now.second)

2.4 Creating Specific Dates:

d = datetime.datetime(2025, 12, 25, 10, 30)
print(d)

2.5 Date Arithmetic with timedelta:

tomorrow = now + datetime.timedelta(days=1)
yesterday = now - datetime.timedelta(days=1)
print("Tomorrow:", tomorrow)
print("Yesterday:", yesterday)

2.6 Comparing Dates:

if tomorrow > now:
    print("Tomorrow is later")

3. The date and time Classes

3.1 date:

from datetime import date

my_date = date(2025, 1, 1)
print(my_date)
print("Weekday:", my_date.weekday())  # 0 = Monday

3.2 time:

from datetime import time

t = time(14, 30, 45)
print(t)

4. Formatting and Parsing Dates

4.1 strftime() — Format Date as String:

formatted = now.strftime("%Y-%m-%d %H:%M:%S")
print(formatted)

Common Format Codes:

• %Y: Year (e.g., 2025)
• %m: Month (01-12)
• %d: Day (01-31)
• %H: Hour (00-23)
• %M: Minute (00-59)
• %S: Second (00-59)

4.2 strptime() — Convert String to Date:

from datetime import datetime

date_str = "2025-07-01 14:30:00"
dt = datetime.strptime(date_str, "%Y-%m-%d %H:%M:%S")
print(dt)

5. Working with Timezones

Timezones can be tricky but are critical for global applications.

5.1 Using pytz:

pip install pytz

import pytz
from datetime import datetime

utc = pytz.utc
india = pytz.timezone("Asia/Kolkata")
now_utc = datetime.now(utc)
now_india = now_utc.astimezone(india)
print("UTC:", now_utc)
print("India:", now_india)

5.2 Using zoneinfo (Python 3.9+):

from zoneinfo import ZoneInfo
from datetime import datetime

now = datetime.now(ZoneInfo("Asia/Kolkata"))
print(now)

6. Using the time Module

Provides lower-level time functions and Unix time support.

6.1 Current Time (Epoch):

import time
print("Current time in seconds:", time.time())

6.2 Sleep (Pause Execution):

time.sleep(2)  # pauses for 2 seconds

6.3 Converting Timestamps:

timestamp = time.time()
date_time = datetime.fromtimestamp(timestamp)
print(date_time)

7. The calendar Module

7.1 Displaying Calendar:

import calendar
print(calendar.month(2025, 5))

7.2 Checking Leap Year:

print(calendar.isleap(2024))  # True

7.3 First Weekday Setting:

calendar.setfirstweekday(calendar.SUNDAY)

8. Real-World Examples

8.1 Logging System:

log_time = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
print(f"[{log_time}] Application started")

8.2 Age Calculator:

from datetime import date

def calculate_age(birthdate):
    today = date.today()
    age = today.year - birthdate.year - ((today.month, today.day) < (birthdate.month, birthdate.day))
    return age

print(calculate_age(date(2000, 7, 15)))

8.3 Countdown Timer:

import time

def countdown(n):
    while n:
        print(n)
        time.sleep(1)
        n -= 1
    print("Time's up!")

countdown(5)

9. Best Practices

• Use datetime for most operations
• Be timezone-aware for global apps
• Always format for user-facing output
• Avoid naive datetime objects in production apps
• Store timestamps in UTC
• Validate and parse input dates carefully

10. Summary

Python’s date and time handling is both powerful and user-friendly, thanks to the datetime, time, and calendar modules. With support for timezone management, formatting, arithmetic, and conversion, you can build robust, time-sensitive applications with ease.

In this chapter, you’ve learned how to:

• Work with datetime, date, and time
• Format and parse date strings
• Handle timezones and daylight savings
• Use calendar for complex scheduling needs
• Apply real-world scenarios like logging, countdowns, and age calculators

✅ Next Chapter: Python for Web Development – Learn how to build web applications using Flask, Django, and other web technologies.