How do I calculate the date in JavaScript three months prior to today?

Navigating through date calculations

Breaking it down, you have to navigate three potential time-travel issues:

1. Month Before Conundrum - Is "three months before" the exact day three months earlier or simply three calendar months prior?
2. Year Transitions Quirk - It handles the back-to-the-future time slips from January to December smoothly.
3. Month-end Time Warp - Even if you time travel from a day that doesn't exist three months ago, JavaScript helps you land safely on the last day of that month.

Addressing edge case scenarios

Avoiding 'day-does-not-exist' dramas

If you're time-traveling from the 31st to a day that doesn't exist three months ago, avoid paradoxes by setting the day to the first.

let date = new Date();
// Avoid being stuck in a time-loop⏱️
date.setDate(1);
date.setMonth(date.getMonth() - 3);


Customizing your time machine

Navigate the quirks of time travel by crafting a custom JavaScript function.

function calculatePastDate(monthsToSubtract) {
    let date = new Date();
    // Let's Go Back in Time!⏳
    date.setMonth(date.getMonth() - monthsToSubtract);
    return date;
}

let threeMonthsPrior = calculatePastDate(3); // Hello, past!


No extra libraries, no external dependencies, just pure JavaScript wizardry!

When to consider third-party libraries?

If basic time-travel isn't enough and you're dealing with pesky timezones, locales, and complex calculations, it's absolutely ok to call in reinforcements like Moment.js or Date-fns.

Riding the JavaScript Time Machine

When it comes to navigating the time vortex, here's what matters:

Built-in functions vs Libraries - Are you just casually hopping around the time-stream or embarking on a complex, temporal manipulation? In the former case, stick to JavaScript's in-built functions. Else, feel free to use the power of JavaScript libraries.

Challenges during time travel

Leap Years: A wrinkle in time

Leap years sneak an extra day in February, make sure your custom solutions account for Leap days.

Precise past date calculation with today's date

Need precise date calculation? Use this combo of getFullYear(), getMonth() and getDate().

new Date(new Date().getFullYear(), new Date().getMonth() - 3, new Date().getDate());
// Remember, precision is everything when time-traveling!


Picking your Time Machine: Moment.js vs Date-fns

Choose your power armor based on your needs:

• Moment.js: Packs a punch with extensive features, but may be an overkill for simple calculations.
• Date-fns: More modular, modern, and optimized for developers cruising through time.