Comparing
2KB immutable date time library alternative to Moment.js with the same modern API
Primitive and flexible state management for React based on atomic state units.
| Metric | dayjs | jotai |
|---|---|---|
| Ecosystem | npm | npm |
| Difficulty | Intermediate | Beginner ✓ |
| Weekly downloads | 43.9M↑ | 900K |
| Latest version | v1.11.20 | v2.9.3 |
| Recipes | 1 | 2↑ |
dayjs only
Shared
jotai only
Use Day.js when you need date parsing, formatting, arithmetic (add/subtract days/months), or comparisons in browser code where bundle size matters. Its plugin system covers timezones, relative time ('3 hours ago'), duration, and ISO weeks.
React apps needing shared state without prop drilling, derived/computed state that updates automatically, fine-grained re-render control, per-route or per-feature isolated state.
For complex timezone-aware calendar applications, consider Temporal (the upcoming TC39 proposal) or date-fns with explicit timezone handling. Day.js's plugin system can grow large if you need many features.
Non-React environments (Jotai is React-only). Complex state machines (use XState). Apps already committed to Redux with large middleware ecosystems.
dayjs
jotai