Accept more readable date-time format in front matter

[DemianX0]

Is your feature request related to a problem? Please describe.
I'm migrating a blog from Hugo to 11ty. The date: front-matter fields include timestamp in the format "2019-07-02 22:39:39 +0200" (Hugo accepts it), while 11ty expects iso8601 ("2019-07-02T22:39:39+02:00") in Template.js.

While deploying to netlify this is the error message:

2:58:11 PM: Problem writing Eleventy templates: (more in DEBUG output)
2:58:11 PM: > date front matter value (2019-07-02 22:39:39 +0200) is invalid for ./src/<...>.md (Error):
2:58:11 PM:     Error: date front matter value (2019-07-02 22:39:39 +0200) is invalid for ./src/<...>.md
2:58:11 PM:         at Template.getMappedDate (/opt/build/repo/node_modules/@11ty/eleventy/src/Template.js:611:19)

Note: There's no difference in the date syntax, therefore this does not affect dates without a timestamp.

Describe the solution you'd like
For easier readability and migration is it possible to accept the following date: front-matter format: "2019-07-02 22:39:39 +0200"?

Describe alternatives you've considered

• An automatic migration script to convert all date: front-matter in a site to iso8601. If there is such a script, please inform.
• Modifying Template.js only for this deployment. Is this possible with netlify, eg. in the .node-modules folder in the git repo?

Additional context

[okitavera]

Alternative approach; the "automatic migration script"

On linux, you can use sed to replace it :

sed -i -e "s/^date: \([0-9\-]\+\) \([0-9\:]\+\) +\([0-9]\+\)/date: \1T\2+\3/g" /path/to/post.md

and then, you can use file and sed to make a batch changes across multiple child folders :

find "$(pwd)" -type f -iname '*.md' -exec sed -i -e "s/^date: \([0-9\-]\+\) \([0-9\:]\+\) +\([0-9]\+\)/date: \1T\2+\3/g" "{}" \;  

PS: That's if your date value is not quoted like this :

date: 2019-07-02 22:39:39 +0200

[zachleat]

Note if it isn’t a string it does the YAML parsing and if it is a string it does Luxon fromISO https://moment.github.io/luxon/#/parsing?id=iso-8601

via https://www.11ty.dev/docs/dates/

Does eleventyComputed help here? https://www.11ty.dev/docs/data-computed/
The other thing I’d look into is gray-matter options for front matter parsing: https://www.11ty.dev/docs/data-frontmatter-customize/

(sorry for the super late reply!) It does seem unlikely that we’ll add additional date formats for this—sorry!

[zachleat]

Seeing this issue and #867 has me thinking maybe another config hook is needed. Follow along over there!