See the full registry of value sets defined as part of FHIR. validDate

{
  "resourceType" : "StructureDefinition",
  "id" : "identifier-validDate",
  "extension" : [{
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode" : "fhir"
  },
  {
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm",
    "valueInteger" : 1
  },
  {
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status",
    "valueCode" : "trial-use"
  }],
  "url" : "http://hl7.org/fhir/StructureDefinition/identifier-validDate",
  "version" : "5.0.0-snapshot3",
  "name" : "validDate",
  "status" : "draft",
  "experimental" : false,
  "date" : "2015-02-28",
  "publisher" : "Health Level Seven, Inc. - FHIR Core WG",
  "contact" : [{
    "telecom" : [{
      "system" : "url",
      "value" : "http://hl7.org/special/committees/FHIR"
    }]
  }],
  "description" : "Indicates a date on which this identifier value was deemed to apply to this instance.",
  "fhirVersion" : "5.0.0-snapshot3",
  "mapping" : [{
    "identity" : "v2",
    "uri" : "http://hl7.org/v2",
    "name" : "HL7 v2 Mapping"
  },
  {
    "identity" : "rim",
    "uri" : "http://hl7.org/v3",
    "name" : "RIM Mapping"
  }],
  "kind" : "complex-type",
  "abstract" : false,
  "context" : [{
    "type" : "element",
    "expression" : "Identifier"
  }],
  "type" : "Extension",
  "baseDefinition" : "http://hl7.org/fhir/StructureDefinition/Extension",
  "derivation" : "constraint",
  "snapshot" : {
    "element" : [{
      "id" : "Extension",
      "path" : "Extension",
      "short" : "External Identifier associated with this element",
      "definition" : "Indicates a date on which this identifier value was deemed to apply to this instance.",
      "comment" : "When referencing business objects where an identifier might not be globally unique but is instead re-used, allows determination of which object applies (on the presumption that the identifiers on the referenced object have an identifier.period or other metadata that indicates when that identifier was valid for the business object).",
      "min" : 0,
      "max" : "*",
      "base" : {
        "path" : "Extension",
        "min" : 0,
        "max" : "*"
      },
      "constraint" : [{
        "key" : "ele-1",
        "severity" : "error",
        "human" : "All FHIR elements must have a @value or children",
        "expression" : "hasValue() or (children().count() > id.count())",
        "source" : "http://hl7.org/fhir/StructureDefinition/Element"
      },
      {
        "key" : "ext-1",
        "severity" : "error",
        "human" : "Must have either extensions or value[x], not both",
        "expression" : "extension.exists() != value.exists()",
        "source" : "http://hl7.org/fhir/StructureDefinition/Extension"
      }],
      "isModifier" : false,
      "mapping" : [{
        "identity" : "v2",
        "map" : "N/A"
      },
      {
        "identity" : "rim",
        "map" : "n/a"
      }]
    },
    {
      "id" : "Extension.id",
      "path" : "Extension.id",
      "representation" : ["xmlAttr"],
      "short" : "Unique id for inter-element referencing",
      "definition" : "Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.",
      "min" : 0,
      "max" : "1",
      "base" : {
        "path" : "Element.id",
        "min" : 0,
        "max" : "1"
      },
      "type" : [{
        "extension" : [{
          "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type",
          "valueUrl" : "id"
        }],
        "code" : "http://hl7.org/fhirpath/System.String"
      }],
      "isModifier" : false,
      "isSummary" : false,
      "mapping" : [{
        "identity" : "rim",
        "map" : "n/a"
      }]
    },
    {
      "id" : "Extension.extension",
      "path" : "Extension.extension",
      "slicing" : {
        "discriminator" : [{
          "type" : "value",
          "path" : "url"
        }],
        "description" : "Extensions are always sliced by (at least) url",
        "rules" : "open"
      },
      "short" : "Extension",
      "definition" : "An Extension",
      "min" : 0,
      "max" : "0",
      "base" : {
        "path" : "Element.extension",
        "min" : 0,
        "max" : "*"
      },
      "type" : [{
        "code" : "Extension"
      }],
      "constraint" : [{
        "key" : "ele-1",
        "severity" : "error",
        "human" : "All FHIR elements must have a @value or children",
        "expression" : "hasValue() or (children().count() > id.count())",
        "source" : "http://hl7.org/fhir/StructureDefinition/Element"
      },
      {
        "key" : "ext-1",
        "severity" : "error",
        "human" : "Must have either extensions or value[x], not both",
        "expression" : "extension.exists() != value.exists()",
        "source" : "http://hl7.org/fhir/StructureDefinition/Extension"
      }],
      "isModifier" : false,
      "isSummary" : false
    },
    {
      "id" : "Extension.url",
      "path" : "Extension.url",
      "representation" : ["xmlAttr"],
      "short" : "identifies the meaning of the extension",
      "definition" : "Source of the definition for the extension code - a logical name or a URL.",
      "comment" : "The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.",
      "min" : 1,
      "max" : "1",
      "base" : {
        "path" : "Extension.url",
        "min" : 1,
        "max" : "1"
      },
      "type" : [{
        "extension" : [{
          "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type",
          "valueUrl" : "uri"
        }],
        "code" : "http://hl7.org/fhirpath/System.String"
      }],
      "fixedUri" : "http://hl7.org/fhir/StructureDefinition/identifier-validDate",
      "isModifier" : false,
      "isSummary" : false,
      "mapping" : [{
        "identity" : "rim",
        "map" : "N/A"
      }]
    },
    {
      "id" : "Extension.value[x]",
      "path" : "Extension.value[x]",
      "short" : "Value of extension",
      "definition" : "Value of extension - must be one of a constrained set of the data types (see [Extensibility](extensibility.html) for a list).",
      "min" : 1,
      "max" : "1",
      "base" : {
        "path" : "Extension.value[x]",
        "min" : 0,
        "max" : "1"
      },
      "type" : [{
        "code" : "dateTime"
      }],
      "constraint" : [{
        "key" : "ele-1",
        "severity" : "error",
        "human" : "All FHIR elements must have a @value or children",
        "expression" : "hasValue() or (children().count() > id.count())",
        "source" : "http://hl7.org/fhir/StructureDefinition/Element"
      }],
      "isModifier" : false,
      "isSummary" : false,
      "mapping" : [{
        "identity" : "rim",
        "map" : "N/A"
      }]
    }]
  },
  "differential" : {
    "element" : [{
      "id" : "Extension",
      "path" : "Extension",
      "short" : "External Identifier associated with this element",
      "definition" : "Indicates a date on which this identifier value was deemed to apply to this instance.",
      "comment" : "When referencing business objects where an identifier might not be globally unique but is instead re-used, allows determination of which object applies (on the presumption that the identifiers on the referenced object have an identifier.period or other metadata that indicates when that identifier was valid for the business object).",
      "min" : 0,
      "max" : "*",
      "mapping" : [{
        "identity" : "v2",
        "map" : "N/A"
      },
      {
        "identity" : "rim",
        "map" : "n/a"
      }]
    },
    {
      "id" : "Extension.extension",
      "path" : "Extension.extension",
      "max" : "0"
    },
    {
      "id" : "Extension.url",
      "path" : "Extension.url",
      "fixedUri" : "http://hl7.org/fhir/StructureDefinition/identifier-validDate"
    },
    {
      "id" : "Extension.value[x]",
      "path" : "Extension.value[x]",
      "min" : 1,
      "type" : [{
        "code" : "dateTime"
      }]
    }]
  }
}