How can I convert Date JsonObject to String?

  angular9, symfony4

I want to get the date from an API written with Symfony 4 to Angular 9 but the Json object is in this form what can I do to convert it to string?
Please help!

offset: 7200
timestamp: 1597960800
timezone: {name: "Europe/Berlin", transitions: Array(144), location: {…}}
__proto__: Object

Source: Symfony4 Questions