Arithmetic Operations on datetime objects-Python

The datetime class in the datetime module provide a structured approach in  managing date and time data. It provides a wide range of tools and methods that enable easy manipulation of  dates and time values.

from datetime import datetime

print(datetime.now())

In the above example, we used the now()  class method to get the current date and time values. 

from datetime import datetime

pi_day = datetime(year = 2023, month = 3, day = 14, hour = 11, minute = 30, second = 30, microsecond = 500)

print(pi_day)

Timedelta objects, on the other hand, are used to represent a duration in terms of days, seconds, and microseconds.    

from datetime import timedelta

td = timedelta(days=5, seconds=120, microseconds=50000, milliseconds=3000, minutes=10, hours=3, weeks=1)

print(td)

A timedelta can be defined as a difference between two dates or datetime objects. 

Performing arithmetic operations on datetimes

We can use the standard operators on datetime objects. For example we can add two time to a objects together, subtract one from the other, compare two of them using comparison operators such as '<', '>', and '==', and access their individual components such as year, month, and day using dot notation.

Subtraction

from datetime import datetime

today = datetime.now()

past = datetime(2023, 3, 18)

#This returns a timedelta object
print(today - past)

Whenever we subtract two datetime objects, as in above, a timedelta is returned representing the time between the two days. We can also similarly subtract a timedelta from a datetime to get an earlier datetime.

from datetime import datetime, timedelta

today = datetime.now()
one_day = timedelta(days = 1)


yesterday = today - one_day
print('today:', today)

print('yesterday: ', yesterday)

In the above example we instantiated a timedelta object which holds a duration of one day. On subtracting now with the timdelta we get yesterday's datetime object.

from datetime import datetime, timedelta

today = datetime.now()
one_week = timedelta(weeks = 1)

last_week = today - one_week

print(last_week)

Addition

When we add two datetime objects, the result will be a timedelta object representing the duration of time between the two datetime objects. We can even more usefully add a timedelta object to a datetime object, and the result will be a new datetime object that is the original datetime plus the timedelta duration.

from datetime import datetime, timedelta

today = datetime.now()

one_day = timedelta(days = 1)

tomorrow = today + one_day
print('today: ', today.ctime(), '\n')
print('tomorrow: ', tomorrow.ctime())

from datetime import datetime, timedelta

today = datetime.now()

one_week = timedelta(weeks = 1)

next_week = today + one_week
print('today: ', today.ctime(), '\n')
print('next week: ', next_week.ctime())

Comparing datetimes

We can use comparison operators to compare datetime objects  in order to get the relation between them.

from datetime import datetime, timedelta

one_day = timedelta(days = 1)
two_days = timedelta(days = 2)

today = datetime.now()
yesterday = today - one_day
tomorrow = today + one_day


#use the operators
print(today > tomorrow)
print(today > yesterday)
print(yesterday == (tomorrow - two_days) )