Most apps do not need a full date library, so I built a 2KB one

Most frontend and Node.js apps need date utilities.

But in many projects, the actual needs are pretty small:

• format a date
• parse an ISO string
• add a few days or months
• compare two dates
• get the start or end of a day/week/month
• check weekends or leap years

For those common cases, pulling in a larger date library can feel heavier than necessary.

So I built date-light.

What is date-light?

date-light is a small, zero-dependency date utility library for TypeScript and JavaScript.

It provides 39 common date helpers in about 2.18KB minzipped.

npm install date-light
ts
import { addDays, differenceInDays, format, startOfWeek } from "date-light";

const launch = new Date(2026, 5, 30, 14, 30);
const reminder = addDays(launch, -7);

format(launch, "yyyy-MM-dd HH:mm");
// "2026-06-30 14:30"

format(startOfWeek(launch), "yyyy-MM-dd");
// "2026-06-29"

differenceInDays(launch, reminder);
// 7

You can also try it in the docs/playground site:

https://date-light.flyingsquirrel.me

Why I made it

I like date-fns. It has a great API and covers a huge range of date operations.

But most apps I work on only use a small subset of that surface area.

Common examples:

format(date, "yyyy-MM-dd");
parseISO("2026-01-15");
addDays(date, 7);
addMonths(date, 1);
differenceInDays(a, b);
startOfMonth(date);
endOfMonth(date);
isSameDay(a, b);

I wanted a tiny library that focused on those common operations and avoided everything else:

• no locale system
• no timezone database
• no plugins
• no chainable wrapper
• no runtime dependencies

Just the date helpers most apps actually ship.

What it includes

date-light currently includes helpers for:

All functions are typed and return new Date instances instead of mutating the input.

import { addMonths } from "date-light";

const original = new Date(2026, 0, 31);
const next = addMonths(original, 1);

console.log(original);
// Jan 31, 2026

console.log(next);
// Feb 28, 2026

Handling date edge cases

Dates have a lot of sharp edges, so I added tests for the cases that usually cause problems.

For example, month-end clamping:

addMonths(new Date(2026, 0, 31), 1);
// Feb 28, 2026

addMonths(new Date(2024, 0, 31), 1);
// Feb 29, 2024

Leap years:

isLeapYear(new Date(2024, 0, 1));
// true

isLeapYear(new Date(1900, 0, 1));
// false

isLeapYear(new Date(2000, 0, 1));
// true

And date-only ISO parsing:

parseISO("2026-01-15");
// local midnight, matching date-fns behavior

Package support

The package ships with:

• ESM
• CommonJS
• TypeScript declarations
• zero runtime dependencies
• tree-shakeable exports

The package entrypoints are tested before release.

Size

The current library build is about 2.18KB minzipped.

That is the main goal of the project: keep the useful common date helpers small enough that you do not have to think much about adding them.

What date-light is not

date-light is intentionally not a complete date platform.

It does not try to replace:

• full date-fns
• Luxon
• Temporal
• timezone-aware libraries
• advanced locale formatting

If you need full i18n, timezone conversions, duration objects, or complex calendar logic, you should use a more complete library.

date-light is for the smaller common case:

“I just need the date helpers I use all the time.”

Try it

Docs and playground:

https://date-light.flyingsquirrel.me

GitHub:

https://github.com/flyingsquirrel0419/date-light

npm:

npm install date-light

Example:

import {
  format,
  parseISO,
  addDays,
  differenceInDays,
  startOfMonth,
  endOfMonth,
} from "date-light";

const date = parseISO("2026-06-30");

console.log(format(date, "yyyy-MM-dd"));
console.log(format(startOfMonth(date), "yyyy-MM-dd"));
console.log(format(endOfMonth(date), "yyyy-MM-dd"));
console.log(differenceInDays(addDays(date, 7), date));

If you try it, feedback is welcome.

And if you find the project useful, a GitHub star would help a lot:

https://github.com/flyingsquirrel0419/date-light