Update date format to user local format

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I’m using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

Doc pages have e.g. Last updated on 4/25/2022 by Simen Bekkhus, which is the US locale. This makes the date ambiguous when the date is 1-12. While that would still be the case if the date uses the local locale, at least I’d read it correctly 😅

Reproducible demo

https://github.com/facebook/jest

Steps to reproduce

Look at the bottom of e.g. https://jestjs.io/docs/jest-object#fake-timers

Expected behavior

For non-US locales, that it says Last updated on 25/04/2022 by Simen Bekkhus, like new Intl.DateTimeFormat().format() returns when I run it in the Chrome console. I.e. uses local locale, not US locale.

Actual behavior

It uses US date formatting.

Your environment

• Public source code:
• Public site URL: https://jestjs.io/
• Docusaurus version used: 2.0.0-beta.18
• Environment name and version (e.g. Chrome 89, Node.js 16.4): Chrome 100 (and whatever version of node Netlify uses)
• Operating system and version (e.g. Ubuntu 20.04.2 LTS): macOS 12.13.1

Self-service

• I’d be willing to fix this bug myself.

[slorber]

Will keep this open until we provide more flexibility for users to define how they want to handle blog/doc date formats

See also https://github.com/facebook/docusaurus/pull/7673#issuecomment-1170186409

[Josh-Cena]

I’m not sure what scope you want that ISO format to apply: (a) to all locales, or (b) just to en, or © be a user config?

For (a), I’d say using the locale date format is usually not that ambiguous. e.g. fr would format the date as dd-MM-yyyy which seems reasonable to every French-speaking people (actually, maybe not, since fr-CA formats it as yyyy-MM-dd, so a fair proportion of them don’t format as dd-MM-yyyy). It’s just English that has this complication😅 And for ©, when it comes to i18n, it’s usually not the site creator’s call to say what to display, so a config option doesn’t seem right to me either. So the solutions I can think of are:

• Special-case en (which is the default anyways, so it is already special in some sense) where we always use yyyy-MM-dd
• Update the date format after hydration

Both seem like good ways out, but the second way could potentially solve other edge-cases if there are other diverging date formats in other locales that I’m not aware of.