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Python Date and Time: datetime, timedelta, strftime and Time Zones

Learn Python's datetime module: create dates and times, get today's date, format with strftime, parse strings with strptime, add days with timedelta, calculate differences and ages, and handle time zones.

Intermediate7 min readUpdated
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Dates and times appear in almost every real program: order dates, deadlines, birthdays, log timestamps. Python's built-in datetime module represents them as proper objects you can compare, format, and do arithmetic with.

The main types#

TypeHoldsExample
datea calendar date2026-10-23
datetimea date and a time2026-10-23 14:30:05
timea time of day14:30:05
timedeltaa duration30 days
Python
from datetime import date, datetime, timedelta

Creating dates and times#

Python
d = date(2026, 10, 23)
print(d, d.year, d.month, d.day)
print(d.weekday(), d.isoweekday())
Output
2026-10-23 2026 10 23
4 5

weekday() counts Monday as 0; isoweekday() counts Monday as 1. Invalid dates are rejected:

Python
date(2026, 2, 30)
Output
ValueError: day is out of range for month
Python
moment = datetime(2026, 10, 23, 14, 30, 5)
print(moment)
print(moment.date(), moment.time())
Output
2026-10-23 14:30:05
2026-10-23 14:30:05

For the current date and time, use date.today() and datetime.now(). (Their output changes every time you run them, which is why these examples use fixed dates.)

Formatting with strftime#

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

Python
print(d.strftime("%A, %d %B %Y"))
print(moment.strftime("%d/%m/%Y %I:%M %p"))
Output
Friday, 23 October 2026
23/10/2026 02:30 PM
CodeMeaningExample
%Y / %yyear2026 / 26
%mmonth number10
%B / %bmonth name / shortOctober / Oct
%dday of month23
%A / %aweekday / shortFriday / Fri
%Hhour (24-hour)14
%I / %phour (12-hour) / AM-PM02 / PM
%M / %Sminute / second30 / 05

Parsing text with strptime#

strptime ("string parse time") does the reverse, reading text in a known format:

Python
parsed = datetime.strptime("23-10-2026 09:15", "%d-%m-%Y %H:%M")
print(parsed, type(parsed).__name__)

print(datetime.fromisoformat("2026-10-23T09:15:00"))
Output
2026-10-23 09:15:00 datetime
2026-10-23 09:15:00

fromisoformat() is the quickest way to read ISO-formatted strings, which is what most APIs and databases produce.

Date arithmetic with timedelta#

Add or subtract a timedelta to move through time:

Python
d = date(2026, 10, 23)
print(d + timedelta(days=30))
print(d - timedelta(weeks=1))
Output
2026-11-22
2026-10-16

Subtracting two dates gives a timedelta:

Python
start = date(2026, 1, 1)
end = date(2026, 10, 23)
gap = end - start
print(gap, gap.days, type(gap).__name__)
Output
295 days, 0:00:00 295 timedelta

Dates also compare naturally:

Python
d1 = date(2026, 10, 23)
d2 = date(2026, 12, 25)
print(d1 < d2, (d2 - d1).days)
Output
True 63

Calculating age#

Subtract the years, then subtract one more if this year's birthday has not happened yet:

Python
birthday = date(2005, 3, 15)
today = date(2026, 10, 23)

age = today.year - birthday.year - ((today.month, today.day) < (birthday.month, birthday.day))
print(age)
Output
21

The comparison of (month, day) tuples is True (counted as 1) when the birthday is still to come.

Time zones#

A datetime without time zone information is naive. For anything involving users in different places, store times in UTC and convert for display:

Python
from datetime import datetime, timezone
from zoneinfo import ZoneInfo

utc_time = datetime(2026, 10, 23, 9, 0, tzinfo=timezone.utc)
print(utc_time.astimezone(ZoneInfo("Asia/Kolkata")))
Output
2026-10-23 14:30:00+05:30

zoneinfo (Python 3.9+) knows the world's time zones and their daylight-saving rules. On Windows you may need to pip install tzdata for it to find the time zone database.

Common mistakes#

Practice#

Practice exercise

A loan starts on 23 October 2026 with a payment due every 30 days. Print the first four due dates (counting the start date as payment 1) in the format 23 Oct 2026.

Show hint

Loop for i in range(4) and add timedelta(days=30 * i). Format with "%d %b %Y".

Show solution
Python
from datetime import date, timedelta

start = date(2026, 10, 23)
for i in range(4):
    due = start + timedelta(days=30 * i)
    print(i + 1, due.strftime("%d %b %Y"))
Output
1 23 Oct 2026
2 22 Nov 2026
3 22 Dec 2026
4 21 Jan 2027

Because months have 30 or 31 days, "every 30 days" slowly drifts earlier in the month.

Key takeaway#

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