diff --git a/src/extendZod.test.ts b/src/extendZod.test.ts
index faea140..00501dc 100644
--- a/src/extendZod.test.ts
+++ b/src/extendZod.test.ts
@@ -89,4 +89,15 @@ describe('extendZodWithOpenApi', () => {
 
     expect(barString._def.zodOpenApi?.openapi?.effectType).toBe('input');
   });
+
+  it('makes a date input accept strings', () => {
+    const fooString = z.union([z.date().optional(), z.string(), z.null()]);
+
+    const barString = fooString.openapi({
+      description: 'foo',
+      examples: [null, '2021-01-01'],
+    });
+
+    expect(barString._def.zodOpenApi?.openapi?.effectType).toBe('input');
+  });
 });
diff --git a/src/extendZodTypes.ts b/src/extendZodTypes.ts
index af6e16b..b4a69a0 100644
--- a/src/extendZodTypes.ts
+++ b/src/extendZodTypes.ts
@@ -1,20 +1,22 @@
-import type { ZodDate, ZodObject, ZodTypeAny, z } from 'zod';
+import type { ZodObject, ZodTypeAny, z } from 'zod';
 
 import type { CreationType } from './create/components';
 import type { oas30, oas31 } from './openapi3-ts/dist';
 
 type SchemaObject = oas30.SchemaObject & oas31.SchemaObject;
 
+type ReplaceDate<T> = T extends Date ? Exclude<T, Date> | string : T;
+
 /**
  * zod-openapi metadata
  */
 interface ZodOpenApiMetadata<
   T extends ZodTypeAny,
-  TInferred = z.input<T> | z.output<T>,
+  TInferred = Exclude<ReplaceDate<z.input<T> | z.output<T>>, undefined>,
 > extends SchemaObject {
   example?: TInferred;
   examples?: [TInferred, ...TInferred[]];
-  default?: T extends ZodDate ? string : TInferred;
+  default?: TInferred;
   /**
    * Used to set the output of a ZodUnion to be `oneOf` instead of `allOf`
    */