Taming Time: A Guide to Wrangling Dates and Times in JavaScript

Declare Victory Against Finicky Temporal Code

Photo by insung yoon on Unsplash

Dealing with dates and times is necessary in most applications — but date and time manipulation tends to be complicated with lots of edge cases to handle in code.

Thankfully, JavaScript and modern browsers provide some robust built-in APIs for date and time tasks.

However, the date-related parts of JavaScript can still be tricky and unintuitive even for experienced developers.

In this guide, we’ll explore some key challenges around handling dates in JavaScript code along with handy syntax and tips for making the chaos of time a bit more manageable. Let’s dive in!

Common JavaScript Date Pitfalls

Creating and comparing dates in JavaScript often leads to surprising behavior and unintended results if we aren’t careful:

// Using Milliseconds since Epoch 
let d1 = new Date(1645533200000);
let d2 = new Date(1645533200001);

d1 < d2; // False! (uh oh...)

The core JavaScript Date object works under the hood with millisecond timestamps. But this numeric representation often doesn’t map 1:1 with comparisons we want in code.