diff --git a/Directory.Build.props b/Directory.Build.props
index e66b93c..ba3e246 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <VersionPrefix>2.7.0</VersionPrefix>
+    <VersionPrefix>2.8.0</VersionPrefix>
     <LangVersion>11.0</LangVersion>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
@@ -33,7 +33,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <FacilityVersion>2.10.1</FacilityVersion>
+    <FacilityVersion>2.11.0</FacilityVersion>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/ReleaseNotes.md b/ReleaseNotes.md
index 8f1f898..93fb9ec 100644
--- a/ReleaseNotes.md
+++ b/ReleaseNotes.md
@@ -2,6 +2,10 @@
 
 These are the NuGet package releases. See also [npm Release Notes](ReleaseNotesNpm.md).
 
+## 2.8.0
+
+* Support `datetime`.
+
 ## 2.7.0
 
 * Support `extern` data and enum types.
diff --git a/conformance/ConformanceApi.fsd b/conformance/ConformanceApi.fsd
index e51d494..ff35857 100644
--- a/conformance/ConformanceApi.fsd
+++ b/conformance/ConformanceApi.fsd
@@ -149,14 +149,13 @@ service ConformanceApi
 		int32: int32;
 		int64: int64;
 		decimal: decimal;
-
-		[validate]
-		enum: Answer;
+		[validate] enum: Answer;
+		datetime: datetime;
 	}:
 	{
 	}
 
-	[http(method: GET, path: "/checkPath/{string}/{boolean}/{double}/{int32}/{int64}/{decimal}/{enum}")]
+	[http(method: GET, path: "/checkPath/{string}/{boolean}/{double}/{int32}/{int64}/{decimal}/{enum}/{datetime}")]
 	method checkPath
 	{
 		string: string;
@@ -165,9 +164,8 @@ service ConformanceApi
 		int32: int32;
 		int64: int64;
 		decimal: decimal;
-
-		[validate]
-		enum: Answer;
+		[validate] enum: Answer;
+		datetime: datetime;
 	}:
 	{
 	}
@@ -182,6 +180,7 @@ service ConformanceApi
 		[http(from: header)] int64: int64;
 		[http(from: header)] decimal: decimal;
 		[http(from: header)] enum: Answer;
+		[http(from: header)] datetime: datetime;
 	}:
 	{
 		[http(from: header)] string: string;
@@ -191,6 +190,7 @@ service ConformanceApi
 		[http(from: header)] int64: int64;
 		[http(from: header)] decimal: decimal;
 		[http(from: header)] enum: Answer;
+		[http(from: header)] datetime: datetime;
 	}
 
 	[http(path: "/mixed/{path}")]
@@ -261,6 +261,7 @@ service ConformanceApi
 		int32: int32;
 		int64: int64;
 		decimal: decimal;
+		datetime: datetime;
 		bytes: bytes;
 		object: object;
 		error: error;
@@ -280,6 +281,7 @@ service ConformanceApi
 		int32: int32[];
 		int64: int64[];
 		decimal: decimal[];
+		datetime: datetime[];
 		bytes: bytes[];
 		object: object[];
 		error: error[];
@@ -299,6 +301,7 @@ service ConformanceApi
 		int32: map<int32>;
 		int64: map<int64>;
 		decimal: map<decimal>;
+		datetime: map<datetime>;
 		bytes: map<bytes>;
 		object: map<object>;
 		error: map<error>;
@@ -318,6 +321,7 @@ service ConformanceApi
 		int32: result<int32>;
 		int64: result<int64>;
 		decimal: result<decimal>;
+		datetime: result<datetime>;
 		bytes: result<bytes>;
 		object: result<object>;
 		error: result<error>;
@@ -337,6 +341,7 @@ service ConformanceApi
 		int32: nullable<int32>;
 		int64: nullable<int64>;
 		decimal: nullable<decimal>;
+		datetime: nullable<datetime>;
 		bytes: nullable<bytes>;
 		object: nullable<object>;
 		error: nullable<error>;
diff --git a/conformance/ConformanceTests.json b/conformance/ConformanceTests.json
index cb036f7..405be38 100644
--- a/conformance/ConformanceTests.json
+++ b/conformance/ConformanceTests.json
@@ -10,7 +10,8 @@
         "int32": 42,
         "int64": 12345678910,
         "decimal": 1.5,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {}
     },
@@ -24,7 +25,8 @@
         "int32": 42,
         "int64": 12345678910,
         "decimal": 1.5,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {}
     },
@@ -205,6 +207,7 @@
             "int32": [42, 24],
             "int64": [12345678910, -987654321],
             "decimal": [1.5, 6.875],
+            "datetime": ["2001-02-03T04:05:06Z", "2023-08-10T19:41:21Z"],
             "bytes": ["aGk=", ""],
             "object": [{ "": null, " ": [null] }, {}],
             "error": [{ "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } }],
@@ -227,6 +230,7 @@
             "int32": [42, 24],
             "int64": [12345678910, -987654321],
             "decimal": [1.5, 6.875],
+            "datetime": ["2001-02-03T04:05:06Z", "2023-08-10T19:41:21Z"],
             "bytes": ["aGk=", ""],
             "object": [{ "": null, " ": [null] }, {}],
             "error": [{ "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } }],
@@ -252,6 +256,7 @@
           "int32": 42,
           "int64": 12345678910,
           "decimal": 1.5,
+          "datetime": "2001-02-03T04:05:06Z",
           "bytes": "aGk=",
           "object": { "": null, " ": [null] },
           "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } },
@@ -267,6 +272,7 @@
           "int32": 42,
           "int64": 12345678910,
           "decimal": 1.5,
+          "datetime": "2001-02-03T04:05:06Z",
           "bytes": "aGk=",
           "object": { "": null, " ": [null] },
           "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } },
@@ -285,7 +291,8 @@
         "int32": 42,
         "int64": 12345678910,
         "decimal": 1.5,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {
         "string": "string",
@@ -294,7 +301,8 @@
         "int32": 42,
         "int64": 12345678910,
         "decimal": 1.5,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       }
     },
     {
@@ -315,6 +323,7 @@
             "int32": { "": 42, " ": 24 },
             "int64": { "": 12345678910, " ": -987654321 },
             "decimal": { "": 1.5, " ": 6.875 },
+            "datetime": { "": "2001-02-03T04:05:06Z", " ": "2023-08-10T19:41:21Z" },
             "bytes": { "": "aGk=", " ": "" },
             "object": { "": { "": null, " ": [null] }, " ": {} },
             "error": { "": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } }, " ": {} },
@@ -336,6 +345,7 @@
             "int32": { "": 42, " ": 24 },
             "int64": { "": 12345678910, " ": -987654321 },
             "decimal": { "": 1.5, " ": 6.875 },
+            "datetime": { "": "2001-02-03T04:05:06Z", " ": "2023-08-10T19:41:21Z" },
             "bytes": { "": "aGk=", " ": "" },
             "object": { "": { "": null, " ": [null] }, " ": {} },
             "error": { "": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } }, " ": {} },
@@ -361,6 +371,7 @@
             "int32": 42,
             "int64": 12345678910,
             "decimal": 1.5,
+            "datetime": "2001-02-03T04:05:06Z",
             "bytes": "aGk=",
             "object": { "": null, " ": [null] },
             "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } },
@@ -381,6 +392,7 @@
             "int32": 42,
             "int64": 12345678910,
             "decimal": 1.5,
+            "datetime": "2001-02-03T04:05:06Z",
             "bytes": "aGk=",
             "object": { "": null, " ": [null] },
             "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } },
@@ -421,6 +433,7 @@
             "int32": null,
             "int64": null,
             "decimal": null,
+            "datetime": null,
             "bytes": null,
             "object": null,
             "error": null,
@@ -441,6 +454,7 @@
             "int32": null,
             "int64": null,
             "decimal": null,
+            "datetime": null,
             "bytes": null,
             "object": null,
             "error": null,
@@ -465,6 +479,7 @@
             "int32": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "int64": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "decimal": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
+            "datetime": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "bytes": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "object": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "error": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
@@ -485,6 +500,7 @@
             "int32": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "int64": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "decimal": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
+            "datetime": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "bytes": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "object": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
             "error": { "error": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
@@ -509,6 +525,7 @@
             "int32": { "value": 42 },
             "int64": { "value": 12345678910 },
             "decimal": { "value": 1.5 },
+            "datetime": { "value": "2001-02-03T04:05:06Z" },
             "bytes": { "value": "aGk=" },
             "object": { "value": { "": null, " ": [null] } },
             "error": { "value": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
@@ -530,6 +547,7 @@
             "int32": { "value": 42 },
             "int64": { "value": 12345678910 },
             "decimal": { "value": 1.5 },
+            "datetime": { "value": "2001-02-03T04:05:06Z" },
             "bytes": { "value": "aGk=" },
             "object": { "value": { "": null, " ": [null] } },
             "error": { "value": { "code": "code", "message": "message", "innerError": { "code": "code" }, "details": { "": null, " ": [null] } } },
@@ -767,7 +785,7 @@
       "method": "checkPath",
       "httpRequest": {
         "method": "GET",
-        "path": "/CHECKPATH/pathCase/true/1.5/3/4/0.625/yes"
+        "path": "/CHECKPATH/pathCase/true/1.5/3/4/0.625/yes/2001-02-03T04:05:06Z"
       },
       "request": {
         "string": "pathCase",
@@ -776,7 +794,8 @@
         "int32": 3,
         "int64": 4,
         "decimal": 0.625,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {}
     },
@@ -785,7 +804,7 @@
       "method": "checkPath",
       "httpRequest": {
         "method": "GET",
-        "path": "/checkPath/booleanCase/TRUE/1.5/3/4/0.625/yes"
+        "path": "/checkPath/booleanCase/TRUE/1.5/3/4/0.625/yes/2001-02-03T04:05:06Z"
       },
       "request": {
         "string": "booleanCase",
@@ -794,7 +813,8 @@
         "int32": 3,
         "int64": 4,
         "decimal": 0.625,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {}
     },
@@ -803,7 +823,7 @@
       "method": "checkQuery",
       "httpRequest": {
         "method": "GET",
-        "path": "/CHECKQUERY?string=pathCase&boolean=true&double=1.5&int32=3&int64=4&decimal=0.625&enum=yes"
+        "path": "/CHECKQUERY?string=pathCase&boolean=true&double=1.5&int32=3&int64=4&decimal=0.625&enum=yes&datetime=2001-02-03T04:05:06Z"
       },
       "request": {
         "string": "pathCase",
@@ -812,7 +832,8 @@
         "int32": 3,
         "int64": 4,
         "decimal": 0.625,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {}
     },
@@ -821,7 +842,7 @@
       "method": "checkQuery",
       "httpRequest": {
         "method": "GET",
-        "path": "/checkQuery?STRING=queryCase&boolean=true&double=1.5&int32=3&int64=4&decimal=0.625&enum=yes"
+        "path": "/checkQuery?STRING=queryCase&boolean=true&double=1.5&int32=3&int64=4&decimal=0.625&enum=yes&datetime=2001-02-03T04:05:06Z"
       },
       "request": {
         "string": "queryCase",
@@ -830,7 +851,8 @@
         "int32": 3,
         "int64": 4,
         "decimal": 0.625,
-        "enum": "yes"
+        "enum": "yes",
+        "datetime": "2001-02-03T04:05:06Z"
       },
       "response": {}
     },
diff --git a/conformance/ts/src/conformanceApi.ts b/conformance/ts/src/conformanceApi.ts
index 814ec7d..e18424a 100644
--- a/conformance/ts/src/conformanceApi.ts
+++ b/conformance/ts/src/conformanceApi.ts
@@ -259,6 +259,7 @@ class ConformanceApiHttpClient implements IConformanceApi {
     request.int64 == null || query.push('int64=' + request.int64.toString());
     request.decimal == null || query.push('decimal=' + request.decimal.toString());
     request.enum == null || query.push('enum=' + request.enum);
+    request.datetime == null || query.push('datetime=' + encodeURIComponent(request.datetime));
     if (query.length) {
       uri = uri + '?' + query.join('&');
     }
@@ -308,7 +309,11 @@ class ConformanceApiHttpClient implements IConformanceApi {
     if (!uriPartEnum) {
       return Promise.resolve(createRequiredRequestFieldError('enum'));
     }
-    const uri = `checkPath/${uriPartString}/${uriPartBoolean}/${uriPartDouble}/${uriPartInt32}/${uriPartInt64}/${uriPartDecimal}/${uriPartEnum}`;
+    const uriPartDatetime = request.datetime != null && encodeURIComponent(request.datetime);
+    if (!uriPartDatetime) {
+      return Promise.resolve(createRequiredRequestFieldError('datetime'));
+    }
+    const uri = `checkPath/${uriPartString}/${uriPartBoolean}/${uriPartDouble}/${uriPartInt32}/${uriPartInt64}/${uriPartDecimal}/${uriPartEnum}/${uriPartDatetime}`;
     const fetchRequest: IFetchRequest = {
       method: 'GET',
     };
@@ -353,6 +358,9 @@ class ConformanceApiHttpClient implements IConformanceApi {
     if (request.enum != null) {
       fetchRequest.headers!['enum'] = request.enum;
     }
+    if (request.datetime != null) {
+      fetchRequest.headers!['datetime'] = request.datetime;
+    }
     return fetchResponse(this._fetch, this._baseUri + uri, fetchRequest, context)
       .then(result => {
         const status = result.response.status;
@@ -392,6 +400,10 @@ class ConformanceApiHttpClient implements IConformanceApi {
         if (headerValue != null) {
           value.enum = headerValue as Answer;
         }
+        headerValue = result.response.headers.get('datetime');
+        if (headerValue != null) {
+          value.datetime = headerValue;
+        }
         return { value: value };
       });
   }
diff --git a/conformance/ts/src/conformanceApiTypes.ts b/conformance/ts/src/conformanceApiTypes.ts
index 05479e4..42586af 100644
--- a/conformance/ts/src/conformanceApiTypes.ts
+++ b/conformance/ts/src/conformanceApiTypes.ts
@@ -165,6 +165,8 @@ export interface ICheckQueryRequest {
   decimal?: number;
 
   enum?: Answer;
+
+  datetime?: string;
 }
 
 /** Response for CheckQuery. */
@@ -186,6 +188,8 @@ export interface ICheckPathRequest {
   decimal?: number;
 
   enum?: Answer;
+
+  datetime?: string;
 }
 
 /** Response for CheckPath. */
@@ -207,6 +211,8 @@ export interface IMirrorHeadersRequest {
   decimal?: number;
 
   enum?: Answer;
+
+  datetime?: string;
 }
 
 /** Response for MirrorHeaders. */
@@ -224,6 +230,8 @@ export interface IMirrorHeadersResponse {
   decimal?: number;
 
   enum?: Answer;
+
+  datetime?: string;
 }
 
 /** Request for Mixed. */
@@ -336,6 +344,8 @@ export interface IAny {
 
   decimal?: number;
 
+  datetime?: string;
+
   bytes?: string;
 
   object?: { [name: string]: any };
@@ -368,6 +378,8 @@ export interface IAnyArray {
 
   decimal?: number[];
 
+  datetime?: string[];
+
   bytes?: string[];
 
   object?: { [name: string]: any }[];
@@ -400,6 +412,8 @@ export interface IAnyMap {
 
   decimal?: { [name: string]: number };
 
+  datetime?: { [name: string]: string };
+
   bytes?: { [name: string]: string };
 
   object?: { [name: string]: { [name: string]: any } };
@@ -432,6 +446,8 @@ export interface IAnyResult {
 
   decimal?: IServiceResult<number>;
 
+  datetime?: IServiceResult<string>;
+
   bytes?: IServiceResult<string>;
 
   object?: IServiceResult<{ [name: string]: any }>;
@@ -464,6 +480,8 @@ export interface IAnyNullable {
 
   decimal?: (number | null);
 
+  datetime?: (string | null);
+
   bytes?: (string | null);
 
   object?: ({ [name: string]: any } | null);
diff --git a/dotnet-tools.json b/dotnet-tools.json
index 8e16642..9562684 100644
--- a/dotnet-tools.json
+++ b/dotnet-tools.json
@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "facilityconformance": {
-      "version": "2.19.0",
+      "version": "2.21.0",
       "commands": [
         "FacilityConformance"
       ]
diff --git a/src/Facility.CodeGen.JavaScript/JavaScriptGenerator.cs b/src/Facility.CodeGen.JavaScript/JavaScriptGenerator.cs
index d82e0d5..514608c 100644
--- a/src/Facility.CodeGen.JavaScript/JavaScriptGenerator.cs
+++ b/src/Facility.CodeGen.JavaScript/JavaScriptGenerator.cs
@@ -632,6 +632,7 @@ private static string RenderFieldType(ServiceTypeInfo fieldType)
 			{
 				case ServiceTypeKind.String:
 				case ServiceTypeKind.Bytes:
+				case ServiceTypeKind.DateTime:
 					return "string";
 				case ServiceTypeKind.Enum:
 					return fieldType.Enum!.Name;
@@ -676,6 +677,7 @@ private static string RenderUriComponent(ServiceFieldInfo field, ServiceInfo ser
 					return $"request.{fieldName}";
 				case ServiceTypeKind.String:
 				case ServiceTypeKind.Bytes:
+				case ServiceTypeKind.DateTime:
 					return $"encodeURIComponent(request.{fieldName})";
 				case ServiceTypeKind.Boolean:
 				case ServiceTypeKind.Int32:
@@ -703,6 +705,7 @@ private static string ParseFieldValue(ServiceFieldInfo field, ServiceInfo servic
 					return $"{value} as {field.TypeName}";
 				case ServiceTypeKind.String:
 				case ServiceTypeKind.Bytes:
+				case ServiceTypeKind.DateTime:
 					return value;
 				case ServiceTypeKind.Boolean:
 					return $"parseBoolean({value})";
@@ -730,6 +733,7 @@ private static string RenderFieldValue(ServiceFieldInfo field, ServiceInfo servi
 				case ServiceTypeKind.Enum:
 				case ServiceTypeKind.String:
 				case ServiceTypeKind.Bytes:
+				case ServiceTypeKind.DateTime:
 					return value;
 				case ServiceTypeKind.Boolean:
 				case ServiceTypeKind.Int32: