Dayjs

Dayjs is a JavaScript library for parsing, validating, manipulating, and formatting dates and times. It is positioned as a lightweight alternative to Moment.js, offering a similar API but with a substantially smaller footprint. Dayjs emphasizes immutability and a modular design, enabling developers to extend its functionality through plugins.

At its core, Dayjs provides a concise, chainable API for common date operations such as adding or subtracting time, comparing dates, and formatting output. The core object is immutable, meaning operations return new instances rather than mutating the original value.

Parsing and formatting are supported for standard ISO 8601 and RFC 2822 strings, with additional formats available via plugins. The customParseFormat plugin allows parsing from arbitrary formats, while the utc and timezone plugins enable handling of time zones.

Localization is supported through locale data, letting users format dates in different languages. Locales can be loaded and switched at runtime to influence formatting and relative time output.

Dayjs is distributed as an open-source project under the MIT license. It is maintained by a community of contributors on GitHub and is widely used in front-end and Node.js environments where a small, modern date library is desirable.