Given two dates, write a Python program to find the total number of days between them.
Input : dt1 = 13/12/2020, dt2 = 25/2/2021 Output : 74 days Input : dt1 = 01/01/2020, dt2 = 01/01/2021 Output : 366 days
One Naive Solution is to start from dt1 and keep counting days till dt2 is reached. This solution requires more than O(1) time. A Better and Simple solution is to count the total number of days before dt1 from i.e., total days from 00/00/0000 to dt1, then count the total number of days before dt2. Finally, return the difference between the two counts.
# Python3 program two find number of days between two given dates # A date has day 'd', month 'm' and year 'y' class Date: def __init__(self, d, m, y): self.d = d self.m = m self.y = y # To store number of days in all months from # January to Dec. monthDays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] # This function counts number of leap years # before the given date def countLeapYears(d): years = d.y # Check if the current year needs to be considered # for the count of leap years or not if (d.m <= 2): years -= 1 # An year is a leap year if it is a multiple of 4, # multiple of 400 and not a multiple of 100. return int(years / 4) - int(years / 100) + int(years / 400) # This function returns number of days between two # given dates def getDifference(dt1, dt2): # COUNT TOTAL NUMBER OF DAYS BEFORE FIRST DATE 'dt1' # initialize count using years and day n1 = dt1.y * 365 + dt1.d # Add days for months in given date for i in range(0, dt1.m - 1): n1 += monthDays[i] # Since every leap year is of 366 days, # Add a day for every leap year n1 += countLeapYears(dt1) # SIMILARLY, COUNT TOTAL NUMBER OF DAYS BEFORE 'dt2' n2 = dt2.y * 365 + dt2.d for i in range(0, dt2.m - 1): n2 += monthDays[i] n2 += countLeapYears(dt2) # return difference between two counts return (n2 - n1) # Driver program dt1 = Date(13, 12, 2020) dt2 = Date(25, 2, 2021) print(getDifference(dt1, dt2), "days")
Using Python datetime Module:
Python comes with an inbuilt datetime module which helps us to solve various datetime related problems. In order to find the difference between two dates we simply input the two dates with date type and subtract them, which in turn provides us the number of days between the two dates.
# Python3 program two find number of days between two given dates from datetime import date def numOfDays(date1, date2): return (date2-date1).days # Driver program date1 = date(2020, 12, 13) date2 = date(2021, 2, 25) print(numOfDays(date1, date2), "days")