diff --git a/modules/openapi-generator/src/main/resources/Javascript/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Javascript/ApiClient.mustache
index 7fd5f5e6cecd..d618e612b33c 100644
--- a/modules/openapi-generator/src/main/resources/Javascript/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Javascript/ApiClient.mustache
@@ -541,12 +541,15 @@
 {{/usePromises}}  };
 
 {{#emitJSDoc}}  /**
-   * Parses an ISO-8601 string representation of a date value.
+   * Parses an ISO-8601 string representation or epoch representation of a date value.
    * @param {String} str The date value as a string.
    * @returns {Date} The parsed date object.
    */
 {{/emitJSDoc}}  exports.parseDate = function(str) {
-    return new Date(str.replace(/T/i, ' '));
+    if (isNaN(str)) {
+      return new Date(str.replace(/T/i, ' '));
+    }
+    return new Date(+str);
   };
 
 {{#emitJSDoc}}  /**
diff --git a/modules/openapi-generator/src/main/resources/Javascript/es6/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Javascript/es6/ApiClient.mustache
index aa54b3d1bb87..c660001f1fdc 100644
--- a/modules/openapi-generator/src/main/resources/Javascript/es6/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Javascript/es6/ApiClient.mustache
@@ -519,12 +519,15 @@ class ApiClient {
     }
 
     {{#emitJSDoc}}/**
-    * Parses an ISO-8601 string representation of a date value.
+    * Parses an ISO-8601 string representation or epoch representation of a date value.
     * @param {String} str The date value as a string.
     * @returns {Date} The parsed date object.
     */{{/emitJSDoc}}
     static parseDate(str) {
-        return new Date(str);
+        if (isNaN(str)) {
+            return new Date(str);
+        }
+        return new Date(+str);
     }
 
     {{#emitJSDoc}}/**
diff --git a/samples/client/petstore/javascript-es6/src/ApiClient.js b/samples/client/petstore/javascript-es6/src/ApiClient.js
index 91fef65f79b8..3d081bf1877a 100644
--- a/samples/client/petstore/javascript-es6/src/ApiClient.js
+++ b/samples/client/petstore/javascript-es6/src/ApiClient.js
@@ -475,12 +475,15 @@ class ApiClient {
     }
 
     /**
-    * Parses an ISO-8601 string representation of a date value.
+    * Parses an ISO-8601 string representation or epoch representation of a date value.
     * @param {String} str The date value as a string.
     * @returns {Date} The parsed date object.
     */
     static parseDate(str) {
-        return new Date(str);
+        if (isNaN(str)) {
+            return new Date(str);
+        }
+        return new Date(+str);
     }
 
     /**
diff --git a/samples/client/petstore/javascript-promise-es6/src/ApiClient.js b/samples/client/petstore/javascript-promise-es6/src/ApiClient.js
index 9a330d1d6832..d3eb5cb7184f 100644
--- a/samples/client/petstore/javascript-promise-es6/src/ApiClient.js
+++ b/samples/client/petstore/javascript-promise-es6/src/ApiClient.js
@@ -476,12 +476,15 @@ class ApiClient {
     }
 
     /**
-    * Parses an ISO-8601 string representation of a date value.
+    * Parses an ISO-8601 string representation or epoch representation of a date value.
     * @param {String} str The date value as a string.
     * @returns {Date} The parsed date object.
     */
     static parseDate(str) {
-        return new Date(str);
+        if (isNaN(str)) {
+            return new Date(str);
+        }
+        return new Date(+str);
     }
 
     /**