date-fns — Modern Modular JavaScript Date Utility Library

What date-fns Does

• Format — 50+ format tokens, locale-aware
• Parse — strict parsing, ISO, custom formats
• Arithmetic — add/sub days, months, years, hours, minutes, weeks
• Comparison — isAfter, isBefore, isEqual, closestTo
• Difference — differenceInDays/Hours/Minutes
• Distance — formatDistance, formatDistanceToNow (relative strings)
• Locales — 70+ locales
• Timezone — via date-fns-tz adapter
• Immutable — every function returns a new Date

Architecture

Pure functions over native Date objects — no classes, no wrappers. Each function is a separate module. Locales are separate imports for tree-shakeability. Types are native TypeScript (not @types).

Self-Hosting

Client or server library, zero runtime deps.

Key Features

• 200+ pure functions
• Tree-shakeable (v2+)
• TypeScript native
• 70+ locales
• Immutable
• Small (~15KB with common functions)
• No Moment-style mutable object
• ESM and CJS builds
• Native Date compatible

Comparison

FAQ

Q: date-fns or Day.js — which should I choose? A: date-fns is more functional and tree-shakes better; Day.js feels more like Moment with a smoother chainable API. It comes down to personal preference.

Q: How do I handle timezones? A: Use the date-fns-tz companion package, which provides zonedTimeToUtc, formatInTimeZone, and more.

Q: Will I not need it once Temporal ships? A: Temporal isn't fully landed yet (Safari has partial support) and the polyfill is ~60KB. date-fns will remain mainstream for the foreseeable future.

Sources & Credits

• Docs: https://date-fns.org
• GitHub: https://github.com/date-fns/date-fns
• License: MIT