preamble-date-...

# `preamble-date-...`

The `...` header is a date.

## Examples

    error[preamble-date-last-call-deadline]: preamble header `last-call-deadline` is not a date in the `YYYY-MM-DD` format
     --> input.md:8:20
      |
    8 | last-call-deadline: 2020/01/01
      |                    ^^^^^^^^^^^ input contains invalid characters
      |

    error[preamble-date-created]: preamble header `created` is not a date in the `YYYY-MM-DD` format
      --> input.md:10:9
       |
    10 | created: 2020/01/01
       |         ^^^^^^^^^^^ input contains invalid characters
       |

## Explanation

The `preamble-date-...` family of lints make sure that dates in the front matter (or preamble) follow the correct format (`YYYY-MM-DD`.)