TypeScript:
Comparing two dates

How to:

Let’s compare some dates:

const date1 = new Date('2023-04-01T00:00:00Z');
const date2 = new Date('2023-04-02T00:00:00Z');

// Is date1 before date2?
console.log(date1 < date2); // true

// Is date1 the same as date2?
console.log(date1.getTime() === date2.getTime()); // false

// How many days apart?
const diffTime = Math.abs(date2.getTime() - date1.getTime());
const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24)); 
console.log(diffDays); // 1

Sample output:

true
false
1

Deep Dive

Back in the day, dates were a haystack of formats and mangled calculations. With JavaScript (and TypeScript by extension), the Date object simplified things, standardizing how we handle time.

Alternatives? Sure. Libraries like moment.js or date-fns augment date handling with extra functionality. But for basic comparisons? Native Date’s simplicity often does the job.

Under the hood, Date.getTime() gets the milliseconds since epoch (Jan 1, 1970). Comparing these values clears out quirks of time zones and leap seconds, boiling it down to numbers.

See Also

• Mozilla Developer Network Date Reference for the ins and outs of Date objects.
• You Don’t Need Moment.js for times you might, or might not, want a library.
• TypeScript Official Documentation for more on TypeScript’s power and pitfalls.