SWAGGER - Date cannot be represented in JSON Schema - ZOD 4

[VigilioYonatan]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

m\zod@4.2.1\node_modules\zod\v4\core\json-schema-processors.cjs:149
        throw new Error("Date cannot be represented in JSON Schema");
              ^

Error: Date cannot be represented in JSON Schema
    at Object.dateProcessor (C:\Users\user\Desktop\...\node_modules\.pnpm\zod@4.2.1\node_modules\zod\v4\core\json-schema-processors.cjs:149:15)
a

• My zod schema

export const projectSchema = z.object({
	id: z.number().int().positive(),
	demo_url: z.url().nullable(),
	oficial_url: z.url().nullable(),
	repo_url: z.url().nullable(),
	is_repository_private: z.boolean(), 
	start_date: z.coerce.date(),
	end_date: z.coerce.date().nullable(), 
	portfolio_id: z.number().int().positive(),
}).strict();

import { createZodDto } from "nestjs-zod";
import { z } from "zod";
import { projectSchema } from "../schemas/project.schema";

export const projectStoreDto = projectSchema
	.omit({
		id: true,
		created_at: true,
		updated_at: true,
		
	})
	.extend({
		skill_ids: z.array(z.number()).optional(),
	});

export type ProjectStoreDto = z.infer<typeof projectStoreDto>;


export class ProjectStoreDtoClass extends createZodDto(projectStoreDto) {}


// controller
	@ApiOperation({ summary: "Create a new project" })
	@ApiBody({ type: ProjectStoreDtoClass, description: "Project creation data" })
	@ApiResponse({ status: 201, description: "Project created." })
	@UseGuards(AuthenticatedGuard)
	@UsePipes(new ZodPipe(projectStoreDto))
	@Post("/")
	store(@Body() body: ProjectStoreDto) {
		return this.projectService.store(body);
	}

• When i comment this nest swagger main, no error in console

const config = new DocumentBuilder()
		.setTitle("Astro-Test API")
		.setDescription("API documentation for Astro-Test project")
		.setVersion("1.0")
		.addTag("users")
		.build();
	const document = SwaggerModule.createDocument(app, config);

	app.use(
		"/reference",
		apiReference({
			content: document,
		}),
	);

Minimum reproduction code

c

Steps to reproduce

No response

Expected behavior

"@nestjs/common": "^11.1.10",
"@nestjs/config": "^4.0.2",
"@nestjs/core": "^11.1.10",
"@nestjs/swagger": "^11.2.3",
"@scalar/nestjs-api-reference": "^1.0.13",

"typescript": "^5.9.3",
zod": "^4.3.2"

Package version

11.2.3

NestJS version

11.1.10

Node.js version

22.16.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[kamilmysliwiec]

Please provide a minimum reproduction repository (Git repository/StackBlitz/CodeSandbox project).

[NHerndlhofer]

I'm experiencing the same issue after migrating from v3 to v4 - v4 seems to be unable to generate json schemas from z.date() and z.coerce.date() schemas

[kamilmysliwiec]

PRs are more than welcome - if you can reproduce this issue locally

[EzioAuditore12]

I have noticed the same and I founded the cause of the problem, it is occurring when we send our dto into swagger docs, here problem was that in zod v3 we were using z.string.date() but in zod v4 we use z.date() directly, I tried the depreciated way or changing entirely to string and it worked,

1. User Dto

import { z } from 'zod';

import { createZodDto } from 'nestjs-zod';

export const userSchema = z.object({
  id: z.uuid(),
  firstName: z.string().nonempty().max(50),
  middleName: z.string().optional(),
  lastName: z.string().nonempty().max(50),
  phoneNumber: z.string().max(20),
  email: z.email().max(240).optional(),
  expoPushToken: z.string().optional(),
  createdAt: z.date() // Here change to depreciated api z.string().date() for now and it worked
  updatedAt: z.date(),
});

export class UserDto extends createZodDto(userSchema) {}

2. Controller with nestjs swagger

import {
  Controller,
  Get,
  NotFoundException,
  ParseUUIDPipe,
} from '@nestjs/common';
import { Paginate, type PaginateQuery } from 'nestjs-paginate';
import { ApiBody, ApiTags } from '@nestjs/swagger';

import { UserService } from './user.service';

import { plainToInstance } from 'class-transformer';
import { UserDto } from './dto/user.dto';

@ApiTags('User')
@Controller('user')
export class UserController {
  constructor(private readonly userService: UserService) {}

  @Get(':id')
  @ApiBody({type: UserDto}) // Here occured when I was using z.date()
  async findOne(@Param('id', new ParseUUIDPipe()) id: string) {
    const user = await this.userService.findOne(id);

    if (!user) throw new NotFoundException(`User not found with this ${id}`);

    return plainToInstance(UserDto, user);
  }

A fix for now is to change to depreciated api from z.date() to z.string().date() or add a validator package like z.string().refine((val)=> isDate(val)) for now

[NikitaHerndlhofer]

Here is a minimal repo with the reproduction of the issue

Here is how this can be circumvented via overriding the JSONSchema of a specific zod schema. This might be changed in future zod releases, because it uses zod internals.

export function overrideJSONSchema<T>(
  parser: z.ZodType<T>,
  customJSONSchema: unknown,
): z.ZodType<T> {
  const wrappedInstance = parser.meta({});

  wrappedInstance._zod.toJSONSchema = () => {
    return customJSONSchema;
  };
  return wrappedInstance.meta({});
}

/**
 * Creates a date parser that:
 * - Accepts Date objects or ISO datetime strings
 * - Coerces to Date object at runtime
 * - Outputs proper JSON Schema (string with date-time format) for Swagger
 *
 * Note: This will be fixed in the future in nest-zod or zodV4. It's a workaround for now.
 */
export function dateTime(): z.ZodType<Date> {
  return overrideJSONSchema(
    z.union([z.date(), z.iso.datetime().pipe(z.coerce.date())]),
    z.toJSONSchema(z.iso.datetime()),
  );
}

And then you just use the dateTime in your zod schemas.

If I will get some more time, I will probably have a look into this either here, on in the zodv4 repo

[EzioAuditore12]

Here is a minimal repo with the reproduction of the issue

Here is how this can be circumvented via overriding the JSONSchema of a specific zod schema. This might be changed in future zod releases, because it uses zod internals.

export function overrideJSONSchema(
parser: z.ZodType,
customJSONSchema: unknown,
): z.ZodType {
const wrappedInstance = parser.meta({});

wrappedInstance._zod.toJSONSchema = () => {
return customJSONSchema;
};
return wrappedInstance.meta({});
}

/**

• Creates a date parser that:
• • Accepts Date objects or ISO datetime strings
• • Coerces to Date object at runtime
• • Outputs proper JSON Schema (string with date-time format) for Swagger
• Note: This will be fixed in the future in nest-zod or zodV4. It's a workaround for now.
  */
  export function dateTime(): z.ZodType {
  return overrideJSONSchema(
  z.union([z.date(), z.iso.datetime().pipe(z.coerce.date())]),
  z.toJSONSchema(z.iso.datetime()),
  );
  }
  And then you just use the dateTime in your zod schemas.

If I will get some more time, I will probably have a look into this either here, on in the zodv4 repo

It is still giving me same error , I tried using the utility function you provided

D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\json-schema-processors.cjs:154
        throw new Error("Date cannot be represented in JSON Schema");
              ^

Error: Date cannot be represented in JSON Schema
    at Object.dateProcessor (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\json-schema-processors.cjs:154:15)
    at inst._zod.processJSONSchema (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\classic\schemas.cjs:639:69)
    at process (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\to-json-schema.cjs:67:25)
    at D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\json-schema-processors.cjs:357:79
    at Array.map (<anonymous>)
    at Object.unionProcessor (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\json-schema-processors.cjs:357:33)
    at inst._zod.processJSONSchema (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\classic\schemas.cjs:722:69)
    at process (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\to-json-schema.cjs:67:25)
    at Object.objectProcessor (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\core\json-schema-processors.cjs:315:64)
    at inst._zod.processJSONSchema (D:\deploy\KnoziChat-Backend\node_modules\.pnpm\zod@4.3.5\node_modules\zod\v4\classic\schemas.cjs:671:69)

Node.js v24.12.0

Here is my dto

import { z } from 'zod';
import { createZodDto } from 'nestjs-zod';
import { dateTime } from 'src/common/utils/zod-date-time';

export const userSchema = z.object({
  id: z.uuid(),
  firstName: z.string().nonempty().max(50),
  middleName: z.string().nullable().optional(),
  lastName: z.string().nonempty().max(50),
  avatar: z.url().nullable().optional(),
  password: z.string().max(16),
  phoneNumber: z.string().max(20),
  email: z.email().max(240).nullable().optional(),
  expoPushToken: z.string().nullable().optional(),
  createdAt: dateTime(),
  updatedAt: dateTime(),
});

export class UserDto extends createZodDto(userSchema) {}

[fullstackjedi]

I also have the same issue

[kamilmysliwiec]

PRs are more than welcome

[victorperin-visionnaire]

Having the same issue here.

[lukemorales]

For those getting errors for the overrideJSONSchema function, this is the fix:

function overrideJSONSchema<T>(
  parser: z.ZodType<T>,
  customJSONSchema: unknown,
): z.ZodType<T> {
  parser._zod.toJSONSchema = () => customJSONSchema;
  return parser;
}