Changing dates in JavaScript / TypeScript can result in inaccurate dates being displayed after adding days

Question

Changing dates in JavaScript / TypeScript can result in inaccurate dates being displayed after adding days

Recently, I encountered an issue with a simple code snippet that seems to produce inconsistent results. Take a look at the function below:

  addDays(date: Date, days: number): Date {
    console.log('adding ' + days + ' days');
    console.log(date);
    date.setDate(date.getDate() + days);
    console.log(date);
    return date;
  }

Let's see some examples of its output:

Everything seems fine at first:

adding 7 days
error-chart.component.ts:118 Tue Aug 02 2016 00:00:00 GMT+0200 (Vest-Europa (sommertid))
error-chart.component.ts:120 Tue Aug 09 2016 00:00:00 GMT+0200 (Vest-Europa (sommertid))

But then it starts to malfunction:

adding 14 days
error-chart.component.ts:118 Tue Aug 02 2016 00:00:00 GMT+0200 (Vest-Europa (sommertid))
error-chart.component.ts:120 Thu Mar 02 2017 00:00:00 GMT+0100 (Vest-Europa (normaltid))

Suddenly, it jumps ahead by two years:

adding 14 days
error-chart.component.ts:118 Thu Jul 07 2016 00:00:00 GMT+0200 (Vest-Europa (sommertid))
error-chart.component.ts:120 Thu Jun 14 2018 00:00:00 GMT+0200 (Vest-Europa (sommertid))

And then, it continues to exhibit unexpected behavior, now jumping four years:

adding 14 days
error-chart.component.ts:118 Thu Jun 14 2018 00:00:00 GMT+0200 (Vest-Europa (sommertid))
error-chart.component.ts:120 Thu Apr 14 2022 00:00:00 GMT+0200 (Vest-Europa (sommertid))

javascript date datetime time typescript

Answer 1

Answer №1

You seem to be facing an issue with data types. In the scenario where days is set to 14, the correct output should be August 16th. However, if days is assigned as "14", then you will get March 2nd as the result.

Here is a possible solution:

  addDays(date: Date, days: number): Date {
    console.log('adding ' + days + ' days');
    console.log(date);
    date.setDate(date.getDate() + parseInt(days));
    console.log(date);
    return date;
  }

Answer 2

You seem to be facing an issue with data types. In the scenario where days is set to 14, the correct output should be August 16th. However, if days is assigned as "14", then you will get March 2nd as the result.

Here is a possible solution:

  addDays(date: Date, days: number): Date {
    console.log('adding ' + days + ' days');
    console.log(date);
    date.setDate(date.getDate() + parseInt(days));
    console.log(date);
    return date;
  }

Changing dates in JavaScript / TypeScript can result in inaccurate dates being displayed after adding days

Answer №1

Similar questions

Elegant Box 2 - Ascending to the top when clicked

Unexpected error 500 (Internal Server Error) occurred due to BadMethodCallException

Having trouble inserting the current time into Firebase Firestore

Ajax causing unreliable posts

Applying ORM Drizzle in cases of conflict

Generate checkboxes by utilizing the JSON data

The program is designed to only allow up to two images to be wrapped

What is the process for defining default prop data in Next.js?

How to effectively manipulate nested arrays in JavaScript without altering their references

Can default query parameters be predefined for a resource in AngularJS?

Incorporating Javascript jQuery functionalities from an external file

What is the best way to arrange an array to display country data based on Covid cases in descending order rather than alphabetical order?

Can you explain the functionality of this Observable in the context of this Angular 2 example?

Function not functioning as expected in NestJS MongoDB unique field feature

Typescript inheritance results in an undefined value being returned

Leveraging the ReactJS Hook useState for detecting Key press events

As I iterated over the Vehicles API data, I encountered an issue while trying to access specific Vehicle information. I received an error message stating "Cannot read property 'id' of undefined

Omit the <span> tag when exporting to XLS format

Error: Uncaught TypeError - Unable to assign a value to the 'status' property

What is the best way to structure my protractor scenarios for effectively validating HTTP response errors?