diff --git a/packages/typespec-test/test/loadTest/generated/typespec-ts/review/load-testing.api.md b/packages/typespec-test/test/loadTest/generated/typespec-ts/review/load-testing.api.md
index b228924e70..f3d123df32 100644
--- a/packages/typespec-test/test/loadTest/generated/typespec-ts/review/load-testing.api.md
+++ b/packages/typespec-test/test/loadTest/generated/typespec-ts/review/load-testing.api.md
@@ -92,7 +92,7 @@ export interface ErrorDetailsOutput {
 
 // @public
 export interface FileInfo {
-    expireDateTime?: Date | string;
+    expireDateTime?: string;
     fileName?: string;
     fileType?: string;
     url?: string;
@@ -576,8 +576,8 @@ export interface LoadTestAdministrationListTestsQueryParam {
 
 // @public (undocumented)
 export interface LoadTestAdministrationListTestsQueryParamProperties {
-    lastModifiedEndTime?: Date | string;
-    lastModifiedStartTime?: Date | string;
+    lastModifiedEndTime?: string;
+    lastModifiedStartTime?: string;
     maxpagesize?: number;
     orderby?: string;
     search?: string;
@@ -1155,8 +1155,8 @@ export interface LoadTestRunListTestRunsQueryParam {
 
 // @public (undocumented)
 export interface LoadTestRunListTestRunsQueryParamProperties {
-    executionFrom?: Date | string;
-    executionTo?: Date | string;
+    executionFrom?: string;
+    executionTo?: string;
     maxpagesize?: number;
     orderby?: string;
     search?: string;
diff --git a/packages/typespec-test/test/loadTest/generated/typespec-ts/src/models.ts b/packages/typespec-test/test/loadTest/generated/typespec-ts/src/models.ts
index 6cc467751c..e1fadd6aa8 100644
--- a/packages/typespec-test/test/loadTest/generated/typespec-ts/src/models.ts
+++ b/packages/typespec-test/test/loadTest/generated/typespec-ts/src/models.ts
@@ -160,7 +160,7 @@ export interface FileInfo {
    */
   fileType?: string;
   /** Expiry time of the file (ISO 8601 literal format) */
-  expireDateTime?: Date | string;
+  expireDateTime?: string;
   /**
    * Validation status of the file
    *
diff --git a/packages/typespec-test/test/loadTest/generated/typespec-ts/src/parameters.ts b/packages/typespec-test/test/loadTest/generated/typespec-ts/src/parameters.ts
index a6bda7dc18..45b54d2e47 100644
--- a/packages/typespec-test/test/loadTest/generated/typespec-ts/src/parameters.ts
+++ b/packages/typespec-test/test/loadTest/generated/typespec-ts/src/parameters.ts
@@ -47,12 +47,12 @@ export interface LoadTestAdministrationListTestsQueryParamProperties {
    * Start DateTime(ISO 8601 literal format) of the last updated time range to
    * filter tests.
    */
-  lastModifiedStartTime?: Date | string;
+  lastModifiedStartTime?: string;
   /**
    * End DateTime(ISO 8601 literal format) of the last updated time range to filter
    * tests.
    */
-  lastModifiedEndTime?: Date | string;
+  lastModifiedEndTime?: string;
   /** Number of results in response. */
   maxpagesize?: number;
 }
@@ -190,9 +190,9 @@ export interface LoadTestRunListTestRunsQueryParamProperties {
   /** Unique name of an existing load test. */
   testId?: string;
   /** Start DateTime(ISO 8601 literal format) of test-run execution time filter range. */
-  executionFrom?: Date | string;
+  executionFrom?: string;
   /** End DateTime(ISO 8601 literal format) of test-run execution time filter range. */
-  executionTo?: Date | string;
+  executionTo?: string;
   /** Comma separated list of test run status. */
   status?: string;
   /** Number of results in response. */
diff --git a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/models.ts b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/models.ts
index 6cc467751c..e1fadd6aa8 100644
--- a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/models.ts
+++ b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/models.ts
@@ -160,7 +160,7 @@ export interface FileInfo {
    */
   fileType?: string;
   /** Expiry time of the file (ISO 8601 literal format) */
-  expireDateTime?: Date | string;
+  expireDateTime?: string;
   /**
    * Validation status of the file
    *
diff --git a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/parameters.ts b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/parameters.ts
index d9868adf68..351fec5453 100644
--- a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/parameters.ts
+++ b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/rest/parameters.ts
@@ -47,12 +47,12 @@ export interface LoadTestAdministrationListTestsQueryParamProperties {
    * Start DateTime(ISO 8601 literal format) of the last updated time range to
    * filter tests.
    */
-  lastModifiedStartTime?: Date | string;
+  lastModifiedStartTime?: string;
   /**
    * End DateTime(ISO 8601 literal format) of the last updated time range to filter
    * tests.
    */
-  lastModifiedEndTime?: Date | string;
+  lastModifiedEndTime?: string;
   /** Number of results in response. */
   maxpagesize?: number;
 }
@@ -190,9 +190,9 @@ export interface LoadTestRunListTestRunsQueryParamProperties {
   /** Unique name of an existing load test. */
   testId?: string;
   /** Start DateTime(ISO 8601 literal format) of test-run execution time filter range. */
-  executionFrom?: Date | string;
+  executionFrom?: string;
   /** End DateTime(ISO 8601 literal format) of test-run execution time filter range. */
-  executionTo?: Date | string;
+  executionTo?: string;
   /** Comma separated list of test run status. */
   status?: string;
   /** Number of results in response. */
diff --git a/packages/typespec-ts/src/utils/modelUtils.ts b/packages/typespec-ts/src/utils/modelUtils.ts
index deb02f8d77..7c4eb064f0 100644
--- a/packages/typespec-ts/src/utils/modelUtils.ts
+++ b/packages/typespec-ts/src/utils/modelUtils.ts
@@ -1004,7 +1004,7 @@ function getSchemaForStdScalar(
         type: "string",
         format: "date-time",
         description,
-        typeName: "Date | string",
+        typeName: "string",
         outputTypeName: "string"
       };
     case "plainTime":
diff --git a/packages/typespec-ts/test/unit/modelsGenerator.spec.ts b/packages/typespec-ts/test/unit/modelsGenerator.spec.ts
index 99829774ee..a6f8556db6 100644
--- a/packages/typespec-ts/test/unit/modelsGenerator.spec.ts
+++ b/packages/typespec-ts/test/unit/modelsGenerator.spec.ts
@@ -1050,7 +1050,7 @@ describe("Input/output model type", () => {
     });
 
     it("should handle offsetDateTime  -> string in output model &  `Date | string` in input model", async () => {
-      const inputType = "Date | string";
+      const inputType = "string";
       const outputType = "string";
       await verifyPropertyType("offsetDateTime ", inputType, {
         outputType
@@ -1111,7 +1111,7 @@ describe("Input/output model type", () => {
         inputModelFile?.content!,
         `
       export interface SimpleModel { 
-        "createdAt": Date | string;
+        "createdAt": string;
       }
       `
       );
diff --git a/packages/typespec-ts/test/unit/parametersGenerator.spec.ts b/packages/typespec-ts/test/unit/parametersGenerator.spec.ts
index 230a073ac2..0827b660bd 100644
--- a/packages/typespec-ts/test/unit/parametersGenerator.spec.ts
+++ b/packages/typespec-ts/test/unit/parametersGenerator.spec.ts
@@ -87,7 +87,7 @@ describe("Parameters.ts", () => {
         );
       });
 
-      it("should generate offsetDateTime as Date | string", async () => {
+      it("should generate offsetDateTime as string", async () => {
         const parameters = await emitParameterFromTypeSpec(
           `
           model QueryParameter {
@@ -104,7 +104,7 @@ describe("Parameters.ts", () => {
             import { RequestParameters } from "@azure-rest/core-client";
             
             export interface TestQueryParamProperties {
-              executionTo?: Date | string;
+              executionTo?: string;
             }
   
             export interface TestQueryParam {