Working with Dates and Times

Working with dates and times is a common task in Python. The datetime module provides classes for manipulating dates and times. This tutorial covers the basics of datetime, date, time, timedelta, and timezone handling.

The datetime Module

The datetime module is part of Python standard library. You do not need to install anything.

import datetime

Creating Dates and Times

Creating a Specific Date

Use the date class to create a specific date.

import datetime

## Create a specific date
d = datetime.date(2024, 12, 25)
print(d)
## 2024-12-25

Creating a Specific Time

Use the time class for times.

import datetime

## Create a specific time
t = datetime.time(14, 30, 0)
print(t)
## 14:30:00

Creating a datetime with Both Date and Time

Combine date and time into a datetime object.

import datetime

## Create a specific datetime
dt = datetime.datetime(2024, 12, 25, 14, 30, 0)
print(dt)
## 2024-12-25 14:30:00

Getting the Current Date and Time

Use the now() method.

import datetime

now = datetime.datetime.now()
print(now)
## 2024-03-07 10:15:30.123456

today = datetime.date.today()
print(today)
## 2024-03-07

Extracting Components

You can extract year, month, day, hour, minute, second from a datetime.

import datetime

now = datetime.datetime.now()

print(now.year)       # 2024
print(now.month)      # 3
print(now.day)        # 7
print(now.hour)      # 10
print(now.minute)    # 15
print(now.second)    # 30

Formatting Dates and Times

Use strftime to format datetime as string.

import datetime

now = datetime.datetime.now()

## Common format codes
print(now.strftime("%Y-%m-%d"))           # 2024-03-07
print(now.strftime("%d/%m/%Y"))           # 07/03/2024
print(now.strftime("%B %d, %Y"))          # March 07, 2024
print(now.strftime("%I:%M %p"))           # 10:15 AM
print(now.strftime("%Y-%m-%d %H:%M:%S"))  # 2024-03-07 10:15:30

Parsing Strings to Dates

Use strptime to convert string to datetime.

import datetime

date_string = "2024-12-25 14:30:00"
dt = datetime.datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")
print(dt)
## 2024-12-25 14:30:00

Date Arithmetic with timedelta

Use timedelta for date arithmetic.

import datetime

## Add 7 days to a date
today = datetime.date.today()
one_week = datetime.timedelta(days=7)
next_week = today + one_week
print(next_week)
## 2024-03-14

## Subtract 30 days
thirty_days_ago = today - datetime.timedelta(days=30)
print(thirty_days_ago)
## 2024-02-06

Calculating Time Differences

You can subtract two dates or datetimes to get a timedelta.

import datetime

start = datetime.datetime(2024, 1, 1)
end = datetime.datetime(2024, 1, 15)

difference = end - start
print(difference)
## 14 days, 0:00:00
print(difference.days)
## 14

Timezones

Handle timezones with the zoneinfo module (Python 3.9+).

from datetime import datetime, timezone
from zoneinfo import ZoneInfo

## Create timezone-aware datetime
now_utc = datetime.now(timezone.utc)
print(now_utc)
## 2024-03-07 10:15:30+00:00

## Convert to different timezone
now_pst = now_utc.astimezone(ZoneInfo("America/Los_Angeles"))
print(now_pst)
## 2024-03-07 02:15:30-08:00

Practical Examples

Age Calculator

import datetime

def calculate_age(birthdate):
    today = datetime.date.today()
    age = today.year - birthdate.year
    # Check if birthday hasnt happened yet this year
    if (today.month, today.day) < (birthdate.month, birthdate.day):
        age -= 1
    return age

birth = datetime.date(1990, 5, 15)
print(calculate_age(birth))
## 34 (if today is March 7, 2024)

Days Until Event

import datetime

def days_until(event_date):
    today = datetime.date.today()
    return (event_date - today).days

christmas = datetime.date(2024, 12, 25)
print(f"Days until Christmas: {days_until(christmas)}")
## Days until Christmas: 293

Common Mistakes

Forgetting timezone info

Always specify timezone when working with servers or multiple regions.

## Wrong: naive datetime
now = datetime.datetime.now()

## Right: timezone-aware
now = datetime.datetime.now(timezone.utc)

Using string comparison for dates

Always use datetime objects for comparison, not strings.

## Wrong
"2024-01-01" < "2024-12-31"  # lexicographic comparison

## Right
datetime.date(2024, 1, 1) < datetime.date(2024, 12, 31)  # proper date comparison

Next Steps

Now you know how to work with dates and times in Python. Practice by building a simple event countdown timer or a date difference calculator.

For more advanced date handling, explore the pandas library for time series data or the arrow library for easier timezone handling.