Moment.js
Widely-used but now legacy JavaScript date/time library. Parses, validates, manipulates, and displays dates and times. Was the standard for JavaScript date handling for over a decade. Now in maintenance mode — the Moment.js team officially recommends migrating to modern alternatives (date-fns, Luxon, Temporal API). Still found in millions of codebases due to its historical prevalence. Largest problems: mutable API (mutates dates in place), large bundle size (~300KB), no tree-shaking.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Pure utility library — no network, no secrets. Maintenance mode means security patches may be slow. ReDoS vulnerability history — use updated version.
⚡ Reliability
Best When
You're maintaining an existing codebase that already uses Moment.js and migration cost is not justified.
Avoid When
Starting any new project — use date-fns, Luxon, or the native Temporal API instead. Moment.js is in legacy maintenance mode.
Use Cases
- • Maintain existing codebases that already use Moment.js — changing would require significant refactoring
- • Parse and format dates in legacy Node.js applications where bundle size is not a concern
- • Use moment-timezone for timezone-aware date operations in existing Moment.js projects
- • Relative time formatting ('2 hours ago', 'in 3 days') which was Moment.js's killer feature
- • Date arithmetic (add/subtract days/months/years) in server-side Node.js where bundle size is irrelevant
Not For
- • New projects — use date-fns (functional, tree-shakeable) or Luxon (immutable, Intl-based) for new code
- • Frontend/browser apps where bundle size matters — Moment.js adds ~300KB; use date-fns or Temporal
- • TypeScript-heavy projects — Moment.js TypeScript support is incomplete compared to modern alternatives
Interface
Authentication
No authentication — date utility library.
Pricing
Fully free, MIT licensed. In maintenance mode.
Agent Metadata
Known Gotchas
- ⚠ Moment.js is in maintenance mode — new projects should use date-fns or Luxon; Moment.js team recommends against using it for new code
- ⚠ Moment objects are mutable — moment().add(1, 'day') modifies the original object; always clone with .clone() before storing references: const m = original.clone().add(1, 'day')
- ⚠ Bundle size is ~300KB — if used in browser bundles, consider lazy loading or migrating to date-fns which is tree-shakeable
- ⚠ Parsing without explicit format is lenient and may parse unexpected strings — always provide explicit format string: moment('2024-01-15', 'YYYY-MM-DD')
- ⚠ Month indices are 0-based (January = 0) for moment().month() but month() setter uses same 0-based — inconsistency with day-of-month which is 1-based
- ⚠ moment-timezone adds significant bundle size on top of base moment — use Luxon (built on Intl.DateTimeFormat) for timezone handling in new code
Alternatives
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Scores are editorial opinions as of 2026-03-07.