A set of examples working with Python date and time functions, including formatting dates, date calculations, and other common date tasks. See my string format examples for working with python strings.

First off, all examples use the following import, any additional imports needed will be shown with the example.

from datetime import datetime

Creating Date Objects

Typically the first thing you want to do is create a Python date object, either from a known time, or parsing a string.

Create a Specific Date

# now now = datetime.now() # specific date dt1 = datetime(2011, 8, 29) dt2 = datetime(year=2012, month=3, day=2)

Create Date from Timestamp

Create a Python date object from a unix timestamp, a 10-digit number counting seconds from the epoch

ts = 1294204471 dt = datetime.fromtimestamp(ts)

Create Date from Known Format

Create Python date object from a string with a known format use strptime() see format table below for definitions.

str = "2012-10-20" dts = datetime.strptime(str, '%Y-%m-%d')

Create Date from Unknown Format

To create a Python date object from a string with an unknown date format it is best to use the third-party dateutil module. Install using: python -m pip install python-dateutil

import dateutil.parser as parser str1 = "October 11, 2018" str2 = "Oct 11, 2018" str3 = "Oct 11th, 2018" parser.parse(str1) parser.parse(str2) parser.parse(str3) # datetime.datetime(2018, 10, 11, 0, 0)

Date Format Table

Printing dates in various formats is relatively straight forward, here’s one example. Refer to the table below for available formatting symbols and samples.

dt = datetime(2019, 8, 22) dt.strftime("%b %d, %Y") # Aug 22, 2019

Symbol Definition Example %a Weekday name abbreviated Sun, Mon, Tue, … %A Weekday name full Sunday, Monday, Tuesday, … %b Month name abbreviated Jan, Feb, Mar, … %B Month name full January, February, … %c A “random” date and time representation. Fri Jan 15 16:34:00 1999 %d Day of the month [ 01, 31 ] %f Microsecond [ 000000, 999999 ] %H Hour (24h) [ 00, 23 ] %I Hour (12h) [ 01, 12 ] %j Day of the year [ 001, 366 ] %m Month [ 01, 12 ] %M Minute [ 00, 59 ] %p Locale’s equivalent of either AM or PM. [ AM, PM ] %S Second [ 00, 61 ] %U Week number of the year (Sunday first) [ 00, 53 ] %w Weekday number (Sunday=0) [ 0, 6 ] %W Week number of the year (Monday first) [0, 53 ] %x Locale date 01/15/99 %X Locale time 16:34:00 %y Year without century [ 00, 99 ] %Y Year with century 1999 %z UTC offset in the form +HHMM or -HHMM or empty string

%Z Time zone name or empty string

%% A literal ‘%’ character.



Date Calculations and Timedelta

from datetime import timedelta week_later = dt + timedelta(days=7) last_week = dt - timedelta(days=7) in_five_minutes = dt + timedelta(minutes=5)

Valid timedelta properties are:

weeks, days, hours, minutes, seconds, microseconds, milliseconds

You might notice that a “year” timedelta is absent, don’t b tempted to do days=365, this would be off for leap-years. I would recommend something like the following:

st = datetime(year=2011, month=3, day=17) next_year = datetime(year=st.year+1, month=st.month, day=st.day)

Adding and Subtracting Dates

You can add and subtract date objects when doing so they return timedelta objects. Using the timedelta object, you can access the same properties above.

dt1 = datetime(year=2012, month=8, day=23) dt2 = datetime(year=2012, month=8, day=28) td = dt2 - dt1 td.days # 5

Common Date Functions

Here are examples of some commonly used Python date functions.

Yesterday

Use timedelta to create yesterday’s date as a python date object.

from datetime import date, timedelta yesterday = date.today() - timedelta(days=1) yesterday.strftime('%Y-%m-%d') # 2020-02-08

Last Day of the Month

Two solutions, first using datetime and going to the first day of next month and subtracting a day.

from datetime import timedelta now = datetime.now() next_month = datetime(year=now.year, month=now.month+1, day=1) last_day_month = next_month - timedelta(days=1)

Second solution to determine the last day of the month using the calendar module.

import calendar now = datetime.now() range = calendar.monthrange(now.year, now.month) last_day_month = now.replace(day=range[1])

Next Thursday

today = datetime.now() thursday_dow = 4 today_dow = first_day_of_month.strftime("%w") adjustment = ( 7 + thursday_dow - int(today_dow)) % 7 next_thursday = today + timedelta(days=adjustment)

First Monday of the Month

today = datetime.now() first_day_of_month = today.replace(day=1) day_of_week = first_day_of_month.strftime("%w") adjustment = (8 - int(day_of_week) ) % 7 first_monday = first_day_of_month + timedelta(days=adjustment)

Reference