# What changed in date-fns

> 8 changes in date-fns 4 from its official release notes, upgrade guides and advisories: 1 breaking, 1 deprecations, 1 new APIs and options. Each one cited. Sources checked 2026-10-17. HTML: https://unstale.sh/npm/date-fns/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## date-fns 4

### Breaking changes

- CDN source maps were removed from date-fns; users relying on them should switch to @date-fns/cdn. (4.4.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.4.0)

### Deprecations

- CDN scripts are deprecated and will be removed in the next major release; use @date-fns/cdn instead. (4.4.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.4.0)

### New APIs and options

- Introduces a package for CDN usage that includes CDN source maps. (4.4.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.4.0)

### Fixes and other changes

- Corrects the pt locale so its first day of the week is Sunday. (4.3.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.3.0)
- Fixes month parsing for October, November, and December in the zh-CN locale. (4.3.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.3.0)
- Fixes month parsing for October, November, and December in the zh-HK locale. (4.3.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.3.0)
- Fixes month parsing for October, November, and December in the zh-TW locale. (4.3.0) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.3.0)
- Restores type definitions that were missing in v4.2.0 due to a TypeScript misconfiguration. (4.2.1) — [release notes](https://github.com/date-fns/date-fns/releases/tag/v4.2.1)