Day.js: Lightweight and Powerful

If you loved the Moment.js API but hated its 70KB bundle size, then **Day.js** is for you. At only **2KB**, it is a "drop-in" replacement that offers almost identical syntax with a fraction of the weight.

Plugin-Based Architecture

The secret to Day.js's small size is its modularity. The core library only includes the most essential features. If you need advanced functionality like timezone support, relative time ( "2 minutes ago"), or duration math, you simply import a specific plugin.

Immutable and Modern

Like Luxon, Day.js is entirely immutable. It treats Every operation as a transformation that returns a new date instance. It is written in TypeScript and works perfectly with modern module bundlers like Vite and Webpack.

Format Compatibility

Day.js uses the exact same formatting strings as Moment (e.g., `YYYY-MM-DD`), making it incredibly easy to migrate legacy codebases without having to rewrite your entire UI layer.

Conclusion

For projects where bundle size is critical—such as mobile web apps or high-performance landing pages—Day.js is the gold standard. On the Epoch Clock, we appreciate the efficiency of Day.js in turning raw integers into beautiful humans strings.