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date-fns vs Day.js vs Temporal — choosing the right date library
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Temporal stage 4 (2025)
date-fnsdayjsTemporalMoment.jsdate librarybundle size
Problem
The JavaScript Date API is notoriously difficult. Three major alternatives exist and developers are unsure which to choose for new projects.
Solution
date-fns: pure functions, tree-shakeable, immutable, TypeScript-first. Best for bundled apps needing minimal per-function cost.
Day.js: tiny (~2 KB), chainable, Moment.js-compatible. Best for migration from Moment or a small all-in-one need.
Temporal: native API (stage 4, shipping 2025). Best for new code once target environments support it.
Avoid Moment.js: mutable, 72 KB, maintenance mode.
Day.js: tiny (~2 KB), chainable, Moment.js-compatible. Best for migration from Moment or a small all-in-one need.
Temporal: native API (stage 4, shipping 2025). Best for new code once target environments support it.
Avoid Moment.js: mutable, 72 KB, maintenance mode.
Why
Each library trades off bundle size, API ergonomics, tree-shakeability, and immutability differently. Temporal eliminates the need for any library once it ships universally.
Gotchas
- date-fns takes plain Date objects — easy to accidentally mutate in surrounding code
- Day.js plugins must be registered before use or methods silently do nothing
- Temporal is available via @js-temporal/polyfill before native engine support
- All three parse strings differently — always use ISO 8601 inputs
Code Snippets
Three date libraries side by side
// date-fns — tree-shakeable pure functions
import { addDays, format } from 'date-fns';
format(addDays(new Date(), 7), 'yyyy-MM-dd');
// Day.js — chainable
import dayjs from 'dayjs';
dayjs().add(7, 'day').format('YYYY-MM-DD');
// Temporal (polyfill or native)
import { Temporal } from '@js-temporal/polyfill';
Temporal.Now.plainDateISO().add({ days: 7 }).toString();Revisions (0)
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