http://hl7.org/fhir/StructureDefinition/timing-dayOfMonth|4.0.1

When present, this extension indicate that the event actually only occurs on the specified days of the month, on the times as otherwise specified by the timing schedule.
{
  "description": "When present, this extension indicate that the event actually only occurs on the specified days of the month, on the times as otherwise specified by the timing schedule.",
  "package": "hl7.fhir.r4.core@4.0.1",
  "date": "2015-02-28T00:00:00Z",
  "derivation": "constraint",
  "publisher": "Health Level Seven, Inc. - MnM WG",
  "fhirVersion": "4.0.1",
  "name": "dayOfMonth",
  "mapping": [ {
    "uri": "http://hl7.org/v3",
    "name": "RIM Mapping",
    "identity": "rim"
  } ],
  "abstract": false,
  "type": "Extension",
  "experimental": null,
  "resourceType": "StructureDefinition",
  "fhirversion": null,
  "title": "Day Of Month",
  "versionAlgorithmCoding": null,
  "extension": [ {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode": "fhir"
  }, {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm",
    "valueInteger": 1
  } ],
  "status": "draft",
  "id": "7b8c12e4-e574-5f99-9c1e-4ea9cc73e7b2",
  "kind": "complex-type",
  "url": "http://hl7.org/fhir/StructureDefinition/timing-dayOfMonth",
  "identifier": null,
  "context": [ {
    "type": "element",
    "expression": "Timing.repeat"
  } ],
  "versionAlgorithmString": null,
  "fhir_id": null,
  "version": "4.0.1",
  "contact": [ {
    "telecom": [ {
      "value": "http://hl7.org/special/committees/MnM",
      "system": "url"
    } ]
  } ],
  "baseDefinition": "http://hl7.org/fhir/StructureDefinition/Extension"
}