Read modify and write dates with node.js

Question

My goal is open a text.txt with 3 different dates and times in UTC

1. 2020-07-31T21:43:00.000Z
2. 2020-07-30T21:43:00.000Z
3. 2020-07-28T21:43:00.000Z

modify those dates in EST time and write on a text2.txt file

I know how to open text.txt and write the same 3 dates on text2.txt, but I have no idea how to convert the dates under text.txt

// Require the given module 
var fs = require('fs'); 

// Use readFile() method 
fs.readFile('text.txt', 'utf-8', function(err, data) { 

// Write the data read from text.txt 
// to a file text2.txt 
if( !err ) 
fs.writeFile('text2.txt', data, (err)=>{ 
    if( err ) { 
        throw err; 
    } 
}); 
else
throw err; 

});