storybook/docs/_snippets/before-each-in-preview.md

import MockDate from 'mockdate';

export default {
  async beforeEach() {
    MockDate.reset()
  }
};

// Replace your-renderer with the renderer you are using (e.g., react, vue3, angular, etc.)
import { Preview } from '@storybook/your-renderer';
import MockDate from 'mockdate';

const preview: Preview = {
  async beforeEach() {
    MockDate.reset()
  }
};

export default preview;