How to Subtract Dates in TypeScript

When working with TypeScript (or even plain JavaScript), you may occasionally need to subtract two dates to find the difference between them. This guide will help you achieve that, whether you need the difference in milliseconds, seconds, minutes, hours, or days.

1. Basic Date Subtraction in TypeScript

Dates in TypeScript and JavaScript are represented by the Date object. When you subtract two date objects, you get the difference in milliseconds.

const date1 = new Date("2023-01-01");
const date2 = new Date("2023-01-10");

const differenceInMilliseconds = date2.getTime() - date1.getTime();
console.log(differenceInMilliseconds); // 777600000 (This is 9 days in milliseconds)

2. Getting the Difference in Various Units

Days

To get the difference in days:

const differenceInDays = Math.floor(differenceInMilliseconds / (1000 * 60 * 60 * 24));
console.log(differenceInDays); // 9

Hours

To get the difference in hours:

const differenceInHours = Math.floor(differenceInMilliseconds / (1000 * 60 * 60));
console.log(differenceInHours); // 216 (This is 9 days * 24 hours/day)

Minutes

To get the difference in minutes:

const differenceInMinutes = Math.floor(differenceInMilliseconds / (1000 * 60));
console.log(differenceInMinutes); // 12960 (This is 9 days * 24 hours/day * 60 minutes/hour)

Seconds

To get the difference in seconds:

const differenceInSeconds = Math.floor(differenceInMilliseconds / 1000);
console.log(differenceInSeconds); // 777600 (This is 9 days * 24 hours/day * 60 minutes/hour * 60 seconds/minute)

3. Using Third-Party Libraries

Sometimes, working directly with the native Date object can be cumbersome. For more complex operations or easier date manipulation, you might consider using third-party libraries like moment or date-fns.

Using moment

import * as moment from 'moment';

const date1 = moment("2023-01-01");
const date2 = moment("2023-01-10");

const differenceInDays = date2.diff(date1, 'days');
console.log(differenceInDays); // 9

Using date-fns

import { differenceInDays } from 'date-fns';

const date1 = new Date("2023-01-01");
const date2 = new Date("2023-01-10");

const daysDifference = differenceInDays(date2, date1);
console.log(daysDifference); // 9

4. Handling Time Zones

Keep in mind that the Date object in TypeScript/JavaScript uses the system's time zone. If you're working with dates across different time zones, you'll want to ensure consistent and correct calculations. For this, libraries like moment-timezone or specialized date functions in date-fns can be beneficial.

In conclusion, subtracting dates in TypeScript can be achieved using the native Date object or with the help of third-party libraries for more straightforward operations. Remember to handle time zones if necessary.