# Delta Days Calculator in Python

`if __name__ == '__main__':    print("Elon San")"""This programme works on the basic principle of adding days by steps . Firstly Two cases arise ie. Same Year or Different YearFor Same Year We Calculate up to The Last Day of The Month then add the number of days(31/30/28/29) till the final month Then just simply add the number of days in the final monthFor Different Year We Calculate up to Last day on initial month then to the last month of the initial year . Then up to the Final Year considering leap(365/366) Then to the final month . Lastly just add up the days in the final month DONE !!"""def delta_days_calculator(date_initial, date_final):    temp_list = date_initial.split(".", 2)    if len(temp_list) != 3:        print("!!<Invalid Date/Format>!!")        exit()    day_i = int(temp_list)    month_i = int(temp_list)    year_i = int(temp_list)    leap_err = year_i % 4    temp_list = date_final.split(".", 2)    if len(temp_list) != 3:        print("!!<Invalid Date/Format>!!")    day_f = int(temp_list)    month_f = int(temp_list)    year_f = int(temp_list)    if year_i == year_f:        if month_i > month_f:            print(f"{date_initial} comes after {date_final}")            exit()    if year_f < year_i:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if year_i < 0 or year_f < 0:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_i > 12 or month_f > 12:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_i in [1, 3, 5, 7, 8, 10, 12] and day_i > 31:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_i in [4, 6, 9, 11] and day_i > 30:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_i == 2 and day_i > 29 and leap_err == 0:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_i == 2 and day_i > 28 and leap_err != 0:        print(f"!!! Invalid Entry \nDate : {date_initial} doesn't exist")        exit()    if month_f in [1, 3, 5, 7, 8, 10, 12] and day_f > 31:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_f in [4, 6, 9, 11] and day_f > 30:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_f == 2 and day_f > 29 and leap_err == 0:        print(f"!!! Invalid Entry Date {date_initial} doesn't exist")        exit()    if month_f == 2 and day_f > 28 and leap_err != 0:        print(f"!!! Invalid Entry \nDate : {date_initial} doesn't exist")        exit()    result = 0    if year_i == year_f:        if month_i == month_f:            if month_i in [1, 3, 5, 7, 8, 10, 12]:                temporary = day_f - day_i                result = result + temporary            if month_i in [4, 6, 9, 11]:                temporary = day_f - day_i                result = result + temporary            if month_i == 2:                if leap_err == 0:                    temporary = day_f - day_i                    result = result + temporary                elif leap_err != 0:                    temporary = day_f - day_i                    result = result + temporary        else:            if month_i in [1, 3, 5, 7, 8, 10, 12]:                temporary = 31 - day_i                result = result + temporary            if month_i in [4, 6, 9, 11]:                temporary = 30 - day_i                result = result + temporary            if month_i == 2:                if leap_err == 0:                    temporary = 29 - day_i                    result = result + temporary                elif leap_err != 0:                    temporary = 28 - day_i                    result = result + temporary            month_i = month_i + 1            while month_i < month_f:                if month_i in [1, 3, 5, 7, 8, 10, 12]:                    result = result + 31                if month_i in [4, 6, 9, 11]:                    result = result + 30                if month_i == 2:                    if leap_err == 0:                        result = result + 29                    elif leap_err != 0:                        result = result + 28                month_i += 1            result = result + day_f    else:        if month_i in [1, 3, 5, 7, 8, 10, 12]:            temporary = 31 - day_i            result = result + temporary        if month_i in [4, 6, 9, 11]:            temporary = 30 - day_i            result = result + temporary        if month_i == 2:            if leap_err == 0:                temporary = 29 - day_i                result = result + temporary            elif leap_err != 0:                temporary = 28 - day_i                result = result + temporary        month_i = month_i + 1        while month_i <= 12:            if month_i in [1, 3, 5, 7, 8, 10, 12]:                result = result + 31            if month_i in [4, 6, 9, 11]:                result = result + 30            if month_i == 2:                if leap_err == 0:                    result = result + 29                elif leap_err != 0:                    result = result + 28            month_i += 1        year_i = year_i + 1        while year_i < year_f:            if leap_err == 0:                result = result + 366            else:                result = result + 365            year_i += 1        month_i = 1        if month_i == month_f:            result = result + day_f        else:            while month_i < month_f:                if month_i in [1, 3, 5, 7, 8, 10, 12]:                    result = result + 31                if month_i in [4, 6, 9, 11]:                    result = result + 30                if month_i == 2:                    if leap_err == 0:                        result = result + 29                    elif leap_err != 0:                        result = result + 28                month_i += 1            result = result + day_f    if result == 0:        return f"{date_final} is Tomorrow"    elif result == -1:        return f"{date_initial}={date_final}"    else:        return f"The Number of Days between {date_initial} and {date_final} is \t<{result - 1}>"`