article:published_time (used by Slack and other apps) is unix epoch

[kevinreedy]

On https://www.devopsdays.org/events/2016-kansascity/program/kyle-sexton/, the meta information for published_time is the unix epoch (0001-01-01 00:00:00), which results in a bad date in apps that use this information.

<meta property="article:published_time" content="0001-01-01 00:00:00 &#43;0000 UTC"/>

I also spot checked another link - https://www.devopsdays.org/events/2016-detroit/program/containers-will-not-fix/

[mattstratton]

Oh, snap.

We set that here:
https://github.com/devopsdays/devopsdays-web/blob/master/layouts/partials/head/seo/open_graph.html#L36

But the problem is that .PublishDate isn't set in the frontmatter of anything.

One possible fix would be to change that line to be content="{{ .Date }} instead.

The other fix is to add the PublishDate parameter to frontmatter of everything.

I think that we should actually add PublishDate, because it might be used other places we don't know about. Or better yet, here's what we do:

1. Update the generators/archetypes to include PublishDate
2. put in a conditional to use PublishDate in the meta if it exists, and if not, use Date

[mattstratton]

Did a little bit of digging, and it seems that .PublishDate is generated off of Date, but it's not working for some reason.

Hugo support forums suggested that the problem is we have Date in quotes, which is odd because it comes from the generator.

[mattstratton]

This will be fixed in devopsdays-theme