Post as events

You can add a custom field to posts. Edit your theme’s config.json (or it would be better to create an override copy) and add a new entry under postConfig. Something like:

{
    "name": "myCustomField",
    "label": "Event Date",
    "value": "",
    "type": "text"        
}

It will appear under “Other options” when you edit a post.

Edit – found the relevant doc:

https://getpublii.com/dev/post-config-options/