Day.js is a minimalist JavaScript date and time library that provides a Moment.js-compatible API in a compact footprint. It parses, validates, manipulates, and displays dates and times for modern browsers while maintaining familiarity for developers already using Moment.js.
The library solves the problem of date handling in JavaScript without the overhead of larger alternatives. It achieves this through a minimalist design that keeps the core library extremely small while offering the same modern API patterns developers expect. The tool is immutable, chainable, and supports internationalization through optional locale modules that are only included in your build when explicitly used.
Day.js suits projects where bundle size matters and developers want Moment.js-like ergonomics without the weight penalty. It works well for applications ranging from simple date formatting to complex temporal manipulations. The README positions it explicitly as an alternative to Moment.js, offering the same API surface with significantly reduced overhead. For teams already familiar with Moment.js, adoption requires minimal learning curve since the API is largely compatible.
The project maintains active development with continuous integration checks and test coverage tracking. Plugin architecture allows extending functionality through independent modules without bloating the core library. Internationalization support is built in as an opt-in system rather than a default inclusion. The tool supports all modern browsers and maintains broad compatibility across environments.
