d3/d3-time

d3-time is a JavaScript library that provides a convenient API for performing calendar math, handling the complexities of conventional time units like varying month lengths, leap years, and daylight saving time. It's designed for developers working with data visualization or time-based calculations in JavaScript, particularly those using the D3.js ecosystem. The library simplifies working with dates and times, making it easier to perform operations like finding the next or previous day, week, month, or year.