Convert Squarespace timestamps to real date / time?

I'm trying to make some customizations to the events page, but the timestamps Squarespace provides are somehow strange: 

so e.g. this is

startDate: 1657643425538

If I do 
 

var date1 = new Date(1657643425538).toString()

startDate.toString(date1) // Tue Jul 12 2022 19:30:25 

But the correct date set for the event is Friday 23, 2002, 9 AM.

So what am I doing wrong? or what would be the best way to transform timestamp into correct date / time?

Can you provide a few details about your ultimate goal? What are you trying to change about the Events page?

Also, it is always helpful if you can provide a public link to the page you are working on so that we can see what you're seeing. 

I think timezone has been taken into account, so you have to assign correct timezone to the date value