Issues with 'Error: date front matter value' when date seems valid?

[wholewheattoast]

Describe the bug
I'm in the process of converting a Jekyll site over to Eleventy. When building I'm getting a ton of 'Error: date front matter value' errors for what appear to be valid datetimes in my front matter.

To Reproduce
Steps to reproduce the behavior:

1. run npx @11ty/eleventy
2. see error

~/s/wwt-eleventy (main|…) $ npx @11ty/eleventy
[11ty] Problem writing Eleventy templates: (more in DEBUG output)
[11ty] date front matter value (2015-01-03 22:54:43 GMT) is invalid for ./posts/2015-01-03-how-much-did-you-pay.html (via Error)
[11ty] 
[11ty] Original error stack trace: Error: date front matter value (2015-01-03 22:54:43 GMT) is invalid for ./posts/2015-01-03-how-much-did-you-pay.html
[11ty]     at Template.getMappedDate (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/Template.js:1043:15)
[11ty]     at Template.addPageDate (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/Template.js:453:30)
[11ty]     at Template.getData (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/Template.js:434:31)
[11ty]     at async Template.getTemplateMapEntries (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/Template.js:1087:33)
[11ty]     at async TemplateMap.add (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/TemplateMap.js:59:21)
[11ty]     at async Promise.all (index 1081)
[11ty]     at async TemplateWriter._createTemplateMap (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/TemplateWriter.js:243:5)
[11ty]     at async TemplateWriter.generateTemplates (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/TemplateWriter.js:277:5)
[11ty]     at async TemplateWriter.write (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/TemplateWriter.js:323:23)
[11ty]     at async Eleventy.executeBuild (/Users/shawn/source/wwt-eleventy/node_modules/@11ty/eleventy/src/Eleventy.js:1003:13)
[11ty] Wrote 0 files in 0.86 seconds (v1.0.2)

YAML front matter:

---
layout: post
title: how much did you pay
date: 2015-01-03 22:54:43 GMT
tags: []
tumblr_url: http://wholewheattoast.tumblr.com/post/107046836634/how-much-did-you-pay
source_url: http://instagram.com/p/xaMfKShnK7/
tumblr_img_permalink: 
---

Expected behavior**
Expected the page to build.

Screenshots
YAMLLint seems to think it's valid?

Environment:

• OS and Version: [e.g. Windows/Mac/Linux] MacOS 12.1
• Eleventy Version [via eleventy --version or npx @11ty/eleventy --version] 1.0.2

Additional context
Example from another YAML parser

[pdehaan]

Interesting... The YAMLLint value is quoted, the front matter version isn't.
I'd guess it's choking on the : time separator.
But even w/ quoted date it seems to be giving me an error w/ your string.

Per https://www.11ty.dev/docs/dates/ I think it needs to be a full ISO date that Luxon can parse, like "2015-01-03T22:54:43"

[pdehaan]

https://npm.runkit.com/luxon

const { DateTime}  = require("luxon")
const res = DateTime.fromISO("2015-01-03 22:54:43 GMT");
console.log({res});

"invalid: Invalid {reason: "unparsable", explanation: "the input \"2015-01-03 22:54:43 GMT\" can't be parsed as ISO 8601"}"

[wholewheattoast]

Thank you for the details.

I'd point out that the yaml provided to YAMLLint wasn't quoted, it only returned it that way.
The page does say that,
"
Paste in your YAML and click "Go" - we'll tell you if it's valid or not, and give you a nice clean UTF-8 version of it. Optimized for Ruby.
"

[zachleat]

https://nodeca.github.io/js-yaml/ is what Eleventy uses under the hood!

@pdehaan is right. The date is not a valid YAML date. https://yaml.org/type/timestamp.html

Eleventy does have a fallback for these cases, but it isn’t a valid ISO 8601 either 😅 https://moment.github.io/luxon/#/parsing?id=iso-8601

Content dates docs on 11ty: https://www.11ty.dev/docs/dates/

I think your best bet forward here is to upvote and lobby for #867

Thanks!