Python - Date and Time


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Often in data science we need analysis which is based on temporal values. Python can handle the various formats of date and time gracefully. The datetime library provides necessary methods and functions to handle the following scenarios.

  • Date Time Representation
  • Date Time Arithmetic
  • Date Time Comparison

We will study them one by one.

Date Time Representation

A date and its various parts are represented by using different datetime functions. Also, there are format specifiers which play a role in displaying the alphabetical parts of a date like name of the month or week day. The following code shows today's date and various parts of the date.

import datetime

print 'The Date Today is  :', datetime.datetime.today()

date_today = datetime.date.today()
print date_today
print 'This Year   :', date_today.year
print 'This Month    :', date_today.month
print 'Month Name:',date_today.strftime('%B')
print 'This Week Day    :', date_today.day
print 'Week Day Name:',date_today.strftime('%A')

When we execute the above code, it produces the following result.

The Date Today is  : 2018-04-22 15:38:35.835000
2018-04-22
This Year   : 2018
This Month    : 4
Month Name: April
This Week Day    : 22
Week Day Name: Sunday

Date Time Arithmetic

For calculations involving dates we store the various dates into variables and apply the relevant mathematical operator to these variables.

import datetime 
 
#Capture the First Date
day1 = datetime.date(2018, 2, 12)
print 'day1:', day1.ctime()

# Capture the Second Date
day2 = datetime.date(2017, 8, 18)
print 'day2:', day2.ctime()

# Find the difference between the dates
print 'Number of Days:', day1-day2


date_today  = datetime.date.today() 

# Create a delta of Four Days 
no_of_days = datetime.timedelta(days=4) 

# Use Delta for Past Date
before_four_days = date_today - no_of_days 
print 'Before Four Days:', before_four_days 
 
# Use Delta for future Date
after_four_days = date_today + no_of_days 
print 'After Four Days:', after_four_days 

When we execute the above code, it produces the following result.

day1: Mon Feb 12 00:00:00 2018
day2: Fri Aug 18 00:00:00 2017
Number of Days: 178 days, 0:00:00
Before Four Days: 2018-04-18
After Four Days: 2018-04-26

Date Time Comparison

Date and time are compared using logical operators. But we must be careful in comparing the right parts of the dates with each other. In the below examples we take the future and past dates and compare them using the python if clause along with logical operators.

import datetime

date_today  = datetime.date.today() 

print 'Today is: ', date_today
# Create a delta of Four Days 
no_of_days = datetime.timedelta(days=4) 

# Use Delta for Past Date
before_four_days = date_today - no_of_days 
print 'Before Four Days:', before_four_days 

after_four_days =  date_today + no_of_days

date1 = datetime.date(2018,4,4)

print 'date1:',date1

if date1 == before_four_days :
    print 'Same Dates'
if date_today > date1:
    print 'Past Date'
if date1 < after_four_days:
    print 'Future Date'

When we execute the above code, it produces the following result.

Today is:  2018-04-22
Before Four Days: 2018-04-18
date1: 2018-04-04
Past Date
Future Date

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