date conversion in react-native-library

I have created a react native library. I access the HealthKit features using React Native's NativeModule.

The index.tsx file of my library:

import { NativeModules } from 'react-native';const { MyHealthLibrary } = NativeModules;export default MyHealthLibrary as any;

I install and use this library for my App development.

I want to do the date conversion in the library. I will send Date from my App to this library and the Date needs to be converted to String here in the index.tsx file.

I am very new to this.
How can i do this???