Working with Dates and Time in Python (`datetime` Module)

🟡 Intermediate

📖 Definition

The datetime standard library module provides classes (date, time, datetime, timedelta, timezone) for parsing, formatting, calculating, and manipulating calendar dates, clock times, durations, and time zone timestamps.

🇮🇳 Hindi

Date aur Time tracking ke liye datetime module ka use hota hai. Current date-time ke liye datetime.now(), date differences calculate karne ke liye timedelta, date ko string mein format karne ke liye .strftime(), aur string ko date mein parse karne ke liye .strptime() ka use hota hai.

🚩 Marathi

Date aani time sathi datetime module vaparatat. Formatting sathi .strftime() aani String parsing sathi .strptime() cha wapar kela jato.

📝 1. Core `datetime` Classes

date(year, month, day): Models calendar date (Year, Month, Day).
time(hour, minute, second): Models clock time.
datetime(year, month, day, hour, minute): Combines date and time.
timedelta(days, seconds, ...): Represents duration difference between two dates or times.

from datetime import datetime, date, timedelta

now = datetime.now() # Current date and time
today = date.today() # Current date only

# Adding 14 days duration using timedelta
due_date = today + timedelta(days=14)

📝 2. Formatting (`strftime`) & Parsing (`strptime`)

strftime(format): Converts datetime object -> Formatted String (“String Format Time”).
strptime(string, format): Parses String -> datetime object (“String Parse Time”).

Common Directive Codes:

%Y: 4-digit year (e.g. 2026)
%m: 2-digit month (01-12)
%d: 2-digit day (01-31)
%H: 24-hour hour (00-23)
%M: Minute (00-59)
%S: Second (00-59)
%A: Full weekday name (Sunday)

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

# Parsing
date_obj = datetime.strptime("2026-10-04", "%Y-%m-%d")

💡 Complete Example: Subscription Due Date & Duration Tracker

from datetime import datetime, date, timedelta

print("=== SUBSCRIPTION RENEWAL ENGINE ===")

# 1. Current Date
today = date.today()
subscription_start = date(2026, 10, 1)

# 2. Calculating Expiration Date (30 Days Validity)
subscription_validity = timedelta(days=30)
expiration_date = subscription_start + subscription_validity

# 3. Calculating Remaining Days
days_remaining = (expiration_date - today).days

# 4. Custom Formatting with strftime
formatter = "%d-%b-%Y (%A)"

print(f"Start Date     : {subscription_start.strftime(formatter)}")
print(f"Today's Date   : {today.strftime(formatter)}")
print(f"Expiration Date: {expiration_date.strftime(formatter)}")
print(f"Status         : {days_remaining} Days Remaining")

if days_remaining <= 5:
    print("WARNING        : Subscription renewal due soon!")

👀 Output

=== SUBSCRIPTION RENEWAL ENGINE ===
Start Date     : 01-Oct-2026 (Thursday)
Today's Date   : 04-Oct-2026 (Sunday)
Expiration Date: 31-Oct-2026 (Saturday)
Status         : 27 Days Remaining

⚠️ Common Mistakes

Confusing strftime() (format object to string) with strptime() (parse string to object).
Adding or subtracting integers directly from dates (today + 5 causes a TypeError; use today + timedelta(days=5)!).

🛡️ Safety / Important Notes

For global multi-region applications, work with UTC timestamps using datetime.now(timezone.utc) or explicit timezone libraries (zoneinfo in Python 3.9+) to avoid daylight saving time bugs.

🌍 Real-World Usage

Subscription renewal calculations, audit log timestamps, scheduling tasks, SLA expiration timers, and calendar applications.

🧪 Try It Yourself

Print today’s date formatted as "Day Month Year" (e.g. "04 October 2026").
Calculate the date 100 days from today using timedelta(days=100).

🎯 Mini Challenge

Write a program that takes a birthdate string "2000-05-15", parses it with .strptime(), and calculates the total age in years relative to today.

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Working with Dates and Time in Python (datetime Module)