Algorithm

Your specification doesn't make any sense.
Try again with some examples.

I hate mind reading.

But are you supposed to return the date that 40 days after 1-1-2019?    I note that 40 is not a three digit number.

Does it have to work for 999 which is a three digit number?   If so, do you have to worry about Leap Years?

Is this what you mean:   FromNow( 1-18-2019, 366) = 1-19-2020

Hello,
Example:

Given a date : 1-January-2019
I need to add a number to it , suppose 40
I need to output it as days , month and year

Suppose 1-January-2019, I add a day to it the answer is 2-January -2019

Maybe you want a function that returns the date given an input date and number of days? In JavaScript that is:

const myDate = new Date();
const numberOfDaysToAdd = 40;
myDate.setDate(myDate.getDate() + numberOfDaysToAdd); 
const myFormattedDate = myDate.getDate() + '/'+  myDate.getMonth() + 1 + '/'+ myDate.getFullYear();
console.log(myFormattedDate);

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I would use the moment.js library personally.

Hello Micahel,
Thanks. Can you suggest without adding any functions. Just need a logic algo.

It's really not clear what you are looking for. I think you're going to have to provide some more information and maybe examples.

Are you looking for JavaScript code? Java code? What do you mean by "logic algo"?

This sounds like some sort of homework assignment.

To develop the logic, you should sit down with a calendar and do several examples by hand.
Take notes of what you are doing, and the information you need.  
Things like how many days are in each month.

Thanks. I am looking a logic flowchart and not functions like getDate().
d-glitch - ts not a homework assigment.  I am trying to write a logic flowchart without any inbuilt functions.
Really want something like a flowchart which comes before you code.

One approach to the problem would be to step forward, one day at a time.
You increment the day of the month [and roll over months and years as required] and decrement the number of days until you get to zero.

This would not be efficient.  You could try stepping to the 1st of the next month repeatedly, until you run out of days.

Will not adding 1 to days be the starting point.
Then check whether the days exceed the month days .?

Yes I agree. Thanks

Hi ,
Will you be able to show this in a for loop ?

Thanks

Yes.  
Increment Day = Day +1

Check to see if Month rolls over.  
   No ==> end of loop
  Yes ==> Day = 1    Increment Month = Month + 1

Check to see if Year rolls over.  
   No ==> end of loop
  Yes ==> Month = 1    Increment Year = Year + 1
  ==> end of loop

Checking the end of Month is tricky because Months are different sizes with the added complication of Leap Year.

Thanks,
Can you suggest if I add 40 to todays date what will the output be?

Day 41 is Feb 10th   2-10-2019

Thanks!!!