Day.js

At only 2kB minified and gzipped, it significantly reduces bundle impact compared to Moment.js, as highlighted in the README's badge and description.

Uses the same API patterns as Moment.js, making migration straightforward with minimal code changes, as stated in the project summary.

All operations return new instances, preventing accidental mutations and improving code predictability, a key feature emphasized in the philosophy.

Functionality can be extended via on-demand plugins, allowing customization without bloating the core library, as shown in the plugin examples.

Supports multiple locales that load only when needed, keeping bundles small, as demonstrated in the i18n documentation.