Moment.js

Moment is a JavaScript date and time library that simplifies parsing, formatting, arithmetic, and humanizing of dates. It supports many formats in input and output, internationalization (i18n), locale-based month/day names, relative time (for example, “3 days ago”), and chaining of operations (adding, subtracting, diffing). Developers often use it for calendar displays, scheduling, and manipulating times across time zones or daylight saving transitions. While it makes working with date strings convenient, moment maintains internal mutability, which has trade-offs with safety and chainability. Over time, newer alternatives with immutable and modular designs have emerged, but moment remains widely known and integrated in many legacy projects. Its comprehensive feature set and ease of use made it a standard for date-time handling in JavaScript for many years.