Sample Azure Policy rule to match a specific date format

tag-match-date-policy-rule.json

"parameters": {
  "tagPattern": {
    "type": "String",
    "metadata": {
      "displayName": "Tag pattern",
      "description": "An expressions for \"notMatch\" condition"
    }
  }
  // Other policy parameters...
},
"policyRule": {
  "if": {
    "field": "[[concat('tags[', parameters('tagName'), ']')]", // For example, 'createdDate' as the tag name
    "notMatch": "[[parameters('tagPattern')]" // For example '####-##-##' to match '2023-03-16' as a date format
  },
  "then": {
    // Some policy effect...
  }
}