Python datetime module with examples

In Python, date and time are not a data type of its own, but a module named datetime can be imported to work with the date as well as time. Datetime module comes built into Python, so there is no need to install it externally.

Datetime module supplies classes to work with date and time. These classes provide a number of functions to deal with dates, times and time intervals. Date and datetime are an object in Python, so when you manipulate them, you are actually manipulating objects and not string or timestamps.

The datetime classes are categorize into 6 main classes –

date – An idealized naive date, assuming the current Gregorian calendar always was, and always will be, in effect. Its attributes are year, month and day.
time – An idealized time, independent of any particular day, assuming that every day has exactly 24*60*60 seconds. Its attributes are hour, minute, second, microsecond, and tzinfo.
datetime – Its a combination of date and time along with the attributes year, month, day, hour, minute, second, microsecond, and tzinfo.
timedelta – A duration expressing the difference between two date, time, or datetime instances to microsecond resolution.
tzinfo – It provides time zone information objects.
timezone – A class that implements the tzinfo abstract base class as a fixed offset from the UTC (New in version 3.2).

Date class

When an object of this class is instantiated, it represents a date in the format YYYY-MM-DD. Constructor of this class needs three mandatory arguments year, month and date.

Constructor syntax:

class datetime.date(year, month, day)

The arguments must be in the following range –

MINYEAR <= year <= MAXYEAR
1 <= month <= 12
1 <= day <= number of days in the given month and year

Note – If the argument is not an integer it will raise a TypeError and if it is outside the range a ValueError will be raised.

# Python program to  
# demonstrate date class 
  
# import the date class 
from datetime import date 
  
# initializing constructor 
# and passing arguments in the  
# format year, month, date 
my_date = date(1996, 12, 11) 
  
print("Date passed as argument is", my_date) 
  
# Uncommenting my_date = date(1996, 12, 39) 
# will raise an ValueError as it is 
# outside range 
  
# uncommenting my_date = date('1996', 12, 11) 
# will raise a TypeError as a string is  
# passed instead of interger 

Output:

Date passed as argument is 1996-12-11

Traceback (most recent call last):
  File "/home/ccabfb570d9bd1dcd11dc4fe55fd6ba2.py", line 14, in 
    my_date = date(1996, 12, 39)
ValueError: day is out of range for month

Traceback (most recent call last):
  File "/home/53b974e10651f1853eee3c004b48c481.py", line 18, in 
    my_date = date('1996', 12, 11)
TypeError: an integer is required (got type str)

Current date

To return the current local date today() function of date class is used. today() function comes with several attributes (year, month and day). These can be printed individually.

# Python program to 
# print current date 
  
from datetime import date 
  
# calling the today 
# function of date class 
today = date.today() 
  
print("Today's date is", today) 
  
# Printing date's components 
print("Date components", today.year, today.month, today.day) 

Output:

Today's date is 2019-10-25
Date components 2019 10 25

Different functions available in date class are –

Function name	Description
fromtimestamp(timestamp)	Return the local date corresponding to the POSIX timestamp
fromordinal(ordinal)	Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1.
fromisoformat(date_string)	Return a date corresponding to a date_string given in the format YYYY-MM-DD:
fromisocalendar(year, week, day)	Return a date corresponding to the ISO calendar date specified by year, week and day.

Time class

Time object represents local time, independent of any day.
Constructor Syntax:

class datetime.time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

All the arguments are optional. tzinfo can be None otherwise all the attributes must be integer in the following range –

0 <= hour < 24
0 <= minute < 60
0 <= second < 60
0 <= microsecond < 1000000
fold in [0, 1]

# Python program to 
# demonstrate time class 
  
from datetime import time 
  
# calling the constructor 
my_time = time(13, 24, 56) 
  
print("Entered time", my_time) 
  
# calling constructor with 1  
# argument 
my_time = time(minute = 12) 
print("\nTime with one argument", my_time) 
  
# Calling constructor with  
# 0 argument 
my_time = time() 
print("\nTime without argument", my_time) 
  
# Uncommenting time(hour = 26) 
# will rase an ValueError as  
# it is out of range 
  
# uncommenting time(hour ='23') 
# will raise TypeError as 
# string is passed instead of int 

Output:

Entered time 13:24:56

Time with one argument 00:12:00

Time without argument 00:00:00

Traceback (most recent call last):
  File "/home/95ff83138a1b3e67731e57ec6dddef25.py", line 21, in 
    print(time(hour=26))
ValueError: hour must be in 0..23

Traceback (most recent call last):
  File "/home/fcee9ba5615b0b74fc3ba39ec9a789fd.py", line 21, in 
    print(time(hour='23'))
TypeError: an integer is required (got type str)

After creating a time object, its attributes can also be printed separately.

from datetime import time 
  
Time = time(11, 34, 56) 
  
print("hour =", Time.hour) 
print("minute =", Time.minute) 
print("second =", Time.second) 
print("microsecond =", Time.microsecond) 

Output:

hour = 11
minute = 34
second = 56
microsecond = 0

Datetime class

Information on both date and time is contained in this class. Like a date object, datetime assumes the current Gregorian calendar extended in both directions; like a time object, datetime assumes there are exactly 3600*24 seconds in every day.

Constructor Syntax:

class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

The year, month and day arguments are mandatory. tzinfo can be None, rest all the attributes must be an integer in the following range –

MINYEAR <= year <= MAXYEAR
1 <= month <= 12
1 <= day <= number of days in the given month and year
0 <= hour < 24
0 <= minute < 60
0 <= second < 60
0 <= microsecond < 1000000
fold in [0, 1]

Note – Passing an argument other than integer will raise a TypeError and passign arguments outside the range will raise ValueError.

# Python program to  
# demonstrate datetime object 
  
from datetime import datetime 
  
# Initializing constructor 
a = datetime(1999, 12, 12) 
print(a) 
  
# Initializing constructor  
# with time parameters as well 
a = datetime(1999, 12, 12, 12, 12, 12, 342380) 
print(a) 

Output:

1999-12-12 00:00:00
1999-12-12 12:12:12.342380

After creating a datetime object, its attributes can also be printed separately.

from datetime import datetime 
  
a = datetime(1999, 12, 12, 12, 12, 12) 
  
print("year =", a.year) 
print("month =", a.month) 
print("hour =", a.hour) 
print("minute =", a.minute) 
print("timestamp =", a.timestamp()) 

Output:

year = 1999
month = 12
hour = 12
minute = 12
timestamp = 945000732.0

Current date and time

You can print the current date and time using the now() function. now() function returns the current local date and time.

from datetime import datetime 
  
# Calling now() function 
today = datetime.now() 
  
print("Current date and time is", today) 

Output:

Current date and time is 2019-10-25 11:12:11.289834

Other fucntions of datetime class are –

Fucntion name	Description
utcnow()	Return the current UTC date and time, with tzinfo None.
fromtimestamp(timestamp, tz=None)	Return the local date and time corresponding to the POSIX timestamp.
utcfromtimestamp(timestamp)	Return the UTC datetime corresponding to the POSIX timestamp, with tzinfo None.
fromordinal(ordinal)	Return the datetime corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1.
combine(date, time, tzinfo=self.tzinfo)	Return a new datetime object whose date components are equal to the given date object’s, and whose time components are equal to the given time object’s.
fromisoformat(date_string)	Return a datetime corresponding to a date_string in one of the formats emitted by date.isoformat() and datetime.isoformat().
strptime(date_string, format)	Return a datetime corresponding to date_string, parsed according to format.

Timedelta class

Python timedelta() function is present under datetime library which is generally used for calculating differences in dates and also can be used for date manipulations in Python. It is one of the easiest ways to perform date manipulations.

Constructor syntax:

class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)

Returns : Date

# Timedelta function demonstration   
    
from datetime import datetime, timedelta  
    
    
# Using current time  
ini_time_for_now = datetime.now()  
    
# printing initial_date  
print ("initial_date", str(ini_time_for_now))  
    
# Calculating future dates  
# for two years  
future_date_after_2yrs = ini_time_for_now + timedelta(days = 730)  
    
future_date_after_2days = ini_time_for_now + timedelta(days = 2)  
    
# printing calculated future_dates  
print('future_date_after_2yrs:', str(future_date_after_2yrs))  
print('future_date_after_2days:', str(future_date_after_2days))  

Output:

initial_date 2019-10-25 12:01:01.227848
future_date_after_2yrs: 2021-10-24 12:01:01.227848
future_date_after_2days: 2019-10-27 12:01:01.227848

Time difference can also be found using this class.

# Timedelta function demonstration   
from datetime import datetime, timedelta  
    
# Using current time  
ini_time_for_now = datetime.now()  
    
# printing initial_date  
print ("initial_date", str(ini_time_for_now))  
    
# Some another datetime  
new_final_time = ini_time_for_now + \  
                 timedelta(days = 2)  
    
# printing new final_date  
print ("new_final_time", str(new_final_time))  
    
    
# printing calculated past_dates  
print('Time difference:', str(new_final_time - \  
                             ini_time_for_now))  

Output:

initial_date 2019-10-25 12:02:32.799814
new_final_time 2019-10-27 12:02:32.799814
Time difference: 2 days, 0:00:00

Tzinfo class

This is an abstract base class, meaning that this class should not be instantiated directly. An instance of (a concrete subclass of) tzinfo can be passed to the constructors for datetime and time objects. The latter objects view their attributes as being in local time, and the tzinfo object supports methods revealing offset of local time from UTC, the name of the time zone, and DST offset, all relative to a date or time object passed to them. To know more about this class click here.

Timezone class

The timezone class is a subclass of tzinfo, each instance of which represents a timezone defined by a fixed offset from UTC.

Constructor syntax:

class datetime.timezone(offset, name=None)

The offset argument must be specified as a timedelta object representing the difference between the local time and UTC.

Note – ValueError will be raised if the offset is not in between -timedelta(hours=24) and timedelta(hours=24).

My Personal Notes

Date class

Current date

Time class

Datetime class

Current date and time

Timedelta class

Tzinfo class

Timezone class

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