Unusable date format

date_format says how dates look on the site’s pages, by example: you write one moment, Wednesday 31 December 2025 at 15:04, the way you want every date written, and Statac writes each date the same way. A template can do the same for one date, as {{ page.date | date("December 2025") }}.

Every piece of that moment is a different number or word, so Statac can tell which piece you wrote where: 31 is the day, 12 the month, 2025 the year, 15 or 3 the hour, 04 the minute, and Wednesday the weekday. Something else in the example, such as 1 January 2020, can’t be read, and neither can a piece written twice.

Months and weekdays in words are written in the site’s language, from its file in languages/ or Statac’s own words for it. date_format for the whole site must have the day, the month and the year, the year in full, because every date on the site is written with it.

What you’ll see

error  Unusable date format: `31 December` has no year
  Add the year, which every date on the site is written with.
  More: https://statac.dev/e/unusable-date-format/

In the terminal the message also names the file and line where there is one, and marks the exact text.

Why Statac stops

A format Statac can’t read would put the wrong date, or the same words, on every page.

How to fix it

Write the moment Statac reads: 31 December 2025, with 15:04 or 3.04pm if you want the time. Write the month in the site’s language, or in figures.

Example

In statac.yaml:

date_format: 1 January 2020

The same style, written as 31 December 2025:

date_format: 31 December 2025

A date on 7 March 2026 is then written 7 March 2026.

Its name

Name	unusable-date-format
In the terminal	statac explain unusable-date-format
To stop showing it	It stops the build, so it can't be quietened.