Dates and Time in Python

Python provides the datetime module for working with dates and times. It allows you to manipulate, format, and perform calculations on date and time data.

Importing the datetime Module

from datetime import datetime, timedelta, date

Current Date and Time

Get the Current Date and Time

now = datetime.now()
print(now)  # Output: Current date and time

Get the Current Date

today = date.today()
print(today)  # Output: Current date

Formatting Dates and Times

Default String Representation

now = datetime.now()
print(str(now))  # Output: "2025-01-16 10:15:30.123456"

Custom Formatting with strftime

formatted = now.strftime("%Y-%m-%d %H:%M:%S")
print(formatted)  # Output: "2025-01-16 10:15:30"

Common Formatting Codes:

• %Y: Year (e.g., 2025)
• %m: Month (01 to 12)
• %d: Day of the month (01 to 31)
• %H: Hour (00 to 23)
• %M: Minute (00 to 59)
• %S: Second (00 to 59)
• %A: Full weekday name (e.g., Monday)
• %B: Full month name (e.g., January)

Parsing Strings to Dates

Convert a String to a datetime Object

date_string = "2025-01-16 10:15:30"
parsed_date = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")
print(parsed_date)  # Output: 2025-01-16 10:15:30

Date Arithmetic

Adding and Subtracting Time

now = datetime.now()
future_date = now + timedelta(days=7)
past_date = now - timedelta(days=30)

print(future_date)  # Output: Date 7 days from now
print(past_date)    # Output: Date 30 days ago

Comparing Dates

date1 = datetime(2025, 1, 1)
date2 = datetime(2025, 12, 31)

if date1 < date2:
    print("date1 is earlier than date2")

Working with Time Zones

Using pytz for Time Zones

The pytz library provides support for time zones.

import pytz

utc = pytz.UTC
eastern = pytz.timezone("US/Eastern")

now = datetime.now(utc)
eastern_time = now.astimezone(eastern)

print(eastern_time)  # Output: Current time in US/Eastern timezone

Practical Examples

Calculate Age from a Birthdate

from datetime import date

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

birthdate = date(1990, 5, 20)
print(calculate_age(birthdate))  # Output: Age in years

Countdown to a Specific Date

from datetime import datetime

target_date = datetime(2025, 12, 31)
now = datetime.now()
remaining = target_date - now

print(f"Days remaining: {remaining.days}")

Log with Timestamps

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

Best Practices

1. Use datetime for Date and Time:
   • Use datetime objects instead of strings for date and time operations.
2. Avoid Hardcoding Time Zones:
   • Use libraries like pytz or zoneinfo (Python 3.9+) for managing time zones.
3. Error Handling for Parsing:
   • Use try-except blocks when parsing strings to dates to handle invalid formats.

Practice Exercises

1. Date Formatting:
   • Format the current date as "Day: Monday, Date: 2025-01-16".
2. Date Parsing:
   • Parse the string "16-01-2025" into a datetime object.
3. Date Arithmetic:
   • Write a script that calculates the number of days between two user-provided dates.
4. Age Calculator:
   • Create a program that calculates a person’s age based on their birthdate.

The datetime module is an essential tool for handling dates and times in Python. Its versatility and wide range of features make it ideal for a variety of applications.