date-fns
Comprehensive JavaScript date utility library with a functional programming approach. Unlike Day.js/Moment.js (object-oriented), date-fns exports 200+ pure functions that work with native JavaScript Date objects. Each function is independently importable — perfect tree-shaking. Functions like format(), addDays(), differenceInCalendarDays(), isAfter(), startOfWeek() cover everything date manipulation needs. Called 'Lodash for dates'.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Pure computation library — no network calls. No security concerns. MIT licensed. Zero dependencies.
⚡ Reliability
Best When
You prefer functional programming patterns, need maximum tree-shaking, and want to import only the specific date functions you use.
Avoid When
You want a method-chaining API like Moment.js — use Day.js instead. date-fns's functional style requires passing dates as arguments.
Use Cases
- • Perform date arithmetic (add/subtract days, weeks, months) with pure functions that don't mutate the original Date
- • Format dates in any locale using date-fns/locale packages with format() and formatDistance() functions
- • Calculate date differences (days between dates, is this date after that date) for scheduling and calendar logic
- • Import only the specific date functions you need for optimal tree-shaking and minimal bundle size
- • Use TypeScript's strict date types via date-fns's comprehensive type definitions for compile-time safety
Not For
- • Object-oriented chaining style — use Day.js for a fluent API with method chaining
- • Full timezone database support — date-fns-tz adds timezone support but it's less polished than Luxon's built-in timezone
- • Teams coming from Moment.js wanting identical API — Day.js is the closer API replacement
Interface
Authentication
No authentication — utility library.
Pricing
MIT licensed. Completely free.
Agent Metadata
Known Gotchas
- ⚠ date-fns v3 changed imports — default exports removed; all functions must be named imports; v2 default imports break in v3
- ⚠ JavaScript Date months are 0-indexed (January=0) — date-fns functions follow native Date convention; passing month 1 = February
- ⚠ date-fns does not include timezone support by default — use date-fns-tz package for timezone-aware operations
- ⚠ locale support requires importing locale objects — import { enUS } from 'date-fns/locale'; not automatic from locale string
- ⚠ Native Date is mutable — date-fns functions don't mutate inputs, but developers storing the same Date reference may see unexpected behavior if Date is mutated elsewhere
- ⚠ format() tokens differ from Moment.js (M/D/Y vs m/d/y) — verify format string when migrating from Moment.js
Alternatives
Full Evaluation Report
Comprehensive deep-dive: security analysis, reliability audit, agent experience review, cost modeling, competitive positioning, and improvement roadmap for date-fns.
AI-powered analysis · PDF + markdown · Delivered within 30 minutes
Package Brief
Quick verdict, integration guide, cost projections, gotchas with workarounds, and alternatives comparison.
Delivered within 10 minutes
Score Monitoring
Get alerted when this package's AF, security, or reliability scores change significantly. Stay ahead of regressions.
Continuous monitoring
Scores are editorial opinions as of 2026-03-07.