This is a little snippet to make sure we don't ever use YYYY for date formatting-- this can rarely lead to a very serious bug.

YYYY_considered_harmful.yml

custom_rules:
  YYYY_considered_harmful: # rule identifier
    name: "YYYY considered harmful" # rule name. optional.
    regex: "(YYYY)" # matching pattern
    message: "YYYY means week-year; you probably want yyyy" # violation message. optional.
    severity: error # violation severity. optional.