# What changed in dayjs

> 9 changes in dayjs 1 from its official release notes, upgrade guides and advisories: 1 deprecations. Each one cited. Sources checked 2026-10-18. HTML: https://unstale.sh/npm/dayjs/

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

## dayjs 1

### Deprecations

- Usage warnings were added for diff. (1.11.19) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.19)

### Performance

- Arabic locale functions no longer instantiate regexes, avoiding performance overhead. (1.11.19) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.19)

### Fixes and other changes

- The timezone plugin no longer throws a RangeError for invalid Day.js values. (1.11.23) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.23)
- Fixes timezone offset computation for instance tz() without relying on host DST. (1.11.22) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.22)
- Unsupported year tokens are now preserved in format output. (1.11.21) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.21)
- The Khmer locale now supports meridiem. (1.11.20) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.20)
- The updateLocale plugin merges nested object properties instead of replacing them. (1.11.20) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.20)
- The Belarusian locale was updated with relative time. (1.11.19) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.19)
- The Italian locale phrase “un' ora fa” was replaced with “un'ora fa”. (1.11.19) — [release notes](https://github.com/iamkun/dayjs/releases/tag/v1.11.19)