Dates and Times

Birthdays, deadlines, timestamps, opening hours: dates and times are everywhere. Python's built-in datetime module handles them, including the tricky parts like month lengths and leap years.

The main types

The datetime module has a few classes you'll use all the time:

One naming trap: the module is called datetime, and so is one of the types inside it. That's why you'll see from datetime import datetime, which means "from the datetime module, import the datetime type". If you write import datetime instead, you need the longer datetime.datetime.now() and datetime.date.today(). This lesson uses the from ... import style throughout.

Today and now

from datetime import date, datetime

today = date.today()
now = datetime.now()

print(today)
print(now)
print(today.year, today.month, today.day)
print(now.hour, now.minute)

Your output depends on when, and in which time zone, you run it. Notice that today() belongs to date and now() belongs to datetime. .year, .month, .day, .hour and .minute are plain numbers (no parentheses), so you can use them in calculations.

from datetime import datetime, timezone, timedelta

# None: naive
local = datetime.now()
print(local.tzinfo)

# ends in +00:00
utc_now = datetime.now(timezone.utc)
print(utc_now)

# the same moment, Indian time
india = timezone(timedelta(hours=5, minutes=30))
print(utc_now.astimezone(india))

Creating a specific date

from datetime import date, datetime

moon_landing = date(1969, 7, 20)
meeting = datetime(2026, 3, 14, 15, 30)

print(moon_landing)
print(meeting)

# Monday is 0, Sunday is 6
print(moon_landing.weekday())

# Monday is 1, Sunday is 7
print(moon_landing.isoweekday())

The arguments always go from biggest to smallest: year, month, day, then (for a datetime) hour and minute. datetime(2026, 3, 14, 15, 30) is 14 March 2026 at 3:30 pm. Write the numbers without leading zeros: date(2026, 03, 14) is a SyntaxError. The moon landing was on a Sunday, so weekday() gives 6.

Python checks that dates are real:

from datetime import date

date(2026, 2, 30)

There's no 30 February, so this is a ValueError: "day is out of range for month".

Formatting dates with strftime

strftime() turns a date into text using format codes:

from datetime import datetime

moment = datetime(2026, 3, 14, 15, 9, 26)

print(moment.strftime("%d/%m/%Y"))
print(moment.strftime("%A, %d %B %Y"))
print(moment.strftime("%I:%M %p"))
print(moment.strftime("%Y-%m-%d %H:%M:%S"))
# format codes work in f-strings too
print(f"{moment:%b %d, %Y}")

strftime() gives back a string. The format is a template: each % code is replaced by part of the date, and everything else (/, ,, spaces, words) is copied as it is. So "%d/%m/%Y" gives 14/03/2026.

The most useful codes:

Watch the capitals: %m is the month and %M is the minute; %d is the day and %H is the hour. Mixing up %m and %M is the most common formatting bug.

Parsing text into dates with strptime

strptime() does the opposite: it reads a date from text, using the same codes to describe the layout:

from datetime import datetime

text = "25/12/2026 18:30"
christmas_dinner = datetime.strptime(text, "%d/%m/%Y %H:%M")

print(christmas_dinner)
print(christmas_dinner.strftime("%A"))

The format must describe the text exactly, separators included: / where the text has /, a space where it has a space. A handy way to remember which is which:

If the text doesn't match the format, you get a ValueError. The ISO format YYYY-MM-DD has a shortcut:

from datetime import date

print(date.fromisoformat("2026-07-04"))

Date arithmetic with timedelta

A timedelta is a length of time. Add it to or subtract it from dates:

from datetime import date, timedelta

start = date(2026, 1, 28)

print(start + timedelta(days=7))
print(start + timedelta(weeks=2))
print(start - timedelta(days=30))

Month lengths and leap years are handled for you. Notice how adding a week to January 28 lands on February 4.

timedelta accepts weeks, days, hours, minutes and seconds, but not months or years, because they don't have a fixed length (a month can be 28 to 31 days). To move by months, build a new date, for example start.replace(month=3).

Subtracting two dates gives a timedelta:

from datetime import date

start = date(2026, 1, 1)
end = date(2026, 12, 25)

gap = end - start
print(gap)
print(gap.days, "days")

Printing a timedelta shows days plus hours:minutes:seconds, here 358 days, 0:00:00. .days gives just the number of days, 358, as a plain number you can calculate with.

With datetime values, durations can include hours and minutes:

from datetime import datetime

check_in = datetime(2026, 5, 1, 14, 0)
check_out = datetime(2026, 5, 4, 11, 30)

stay = check_out - check_in
print(stay)
print(stay.total_seconds() / 3600, "hours")

The stay prints as 2 days, 21:30:00. To get it in hours, total_seconds() converts the whole duration to seconds, and dividing by 3600 (seconds in an hour) gives 69.5. Don't use stay.seconds for this: it holds only the leftover part after the whole days (the 21:30:00), not the total.

Comparing dates

Dates compare naturally with <, > and ==, and they sort correctly:

from datetime import date

deadline = date(2026, 6, 30)
submitted = date(2026, 7, 2)

if submitted > deadline:
    late = (submitted - deadline).days
    print(f"Late by {late} days")

dates = [date(2026, 5, 1), date(2025, 12, 31), date(2026, 1, 15)]
print(sorted(dates))

Timing your code

To measure how long something takes, subtract two datetime.now() values, or use time.perf_counter():

import time

start = time.perf_counter()
total = sum(i * i for i in range(1_000_000))
elapsed = time.perf_counter() - start

print(f"Result {total:,} in {elapsed:.3f} seconds")

Exercises

Exercise 1: Day of the week

Print the day of the week you were born, or of any date you like, as a full name such as Thursday.

from datetime import date

birthday = date(2000, 1, 1)

Exercise 2: Due date

A library book is borrowed on 2026-03-25 and is due 21 days later. Print the due date as Due: Wednesday 15 April 2026.

from datetime import date, timedelta

borrowed = date(2026, 3, 25)

Exercise 3: Days until an event

Parse the event date from the string and print how many days there are between today and the event: Days to go: 81.

from datetime import date, datetime

today = date(2026, 10, 5)
event_text = "December 25, 2026"

Exercise 4: Age calculator

Write age_on(birth, on_date) that returns a person's age in whole years on a given date. Remember: if their birthday hasn't happened yet that year, subtract one.

from datetime import date

def age_on(birth, on_date):
    pass

print(age_on(date(1990, 8, 15), date(2026, 8, 14)))   # 35
print(age_on(date(1990, 8, 15), date(2026, 8, 15)))   # 36

Date and time tools at a glance

A quick reference for later. The examples use d = date(2026, 3, 15) and from datetime import date, datetime, timedelta. Results marked "e.g." depend on when you run them. The strftime codes, such as %d and %B, are in the table earlier in this lesson.

Summary

• Import what you need: from datetime import date, datetime, timedelta.
• date.today() and datetime.now() give the current date and time.
• strftime() formats a date as text, and strptime() parses text into a date. Both use codes like %Y, %m and %d.
• Add or subtract a timedelta to move dates. Subtracting two dates gives a timedelta.
• Dates compare and sort naturally.