How to generate future date and time for postman request

{
    "name": "IronMan",
    "phone_number": "555555555",
    "number_of_guest": 10,
    "tables": [
        2
    ],
    "reservation_start_at": "2020-10-15T10:00:00.861873Z",
    "reservation_end": "2020-10-15T11:00:00.861873Z"
}

I am stuck at step where I need to generate future date and time with time zone to send a postman request. The request is about a reservation feature.

On the request body,a key-value is,

"reservation_start_at": "2020-10-15T10:00:00.861873Z"

My question is, how do I generate future date and time for each request?

Thanks in advance .

You can use the following in postman's pre-request script:

var moment = require('moment');

const yearsInTheFuture = 1;
const monthsInTheFuture = 2;
const daysInTheFuture = 3;
const hours = 12;
const minutes = 34;
const seconds = 56;
const milliseconds = 789;
const durationInDays = 7;

const reservation_start_at = moment()
    .add(yearsInTheFuture, 'years')
    .add(monthsInTheFuture, 'months')
    .add(daysInTheFuture, 'days')
    .hours(hours)
    .minutes(minutes)
    .seconds(seconds)
    .millisecond(milliseconds);

reservation_end = moment()
    .add(yearsInTheFuture, 'years')
    .add(monthsInTheFuture, 'months')
    .add(daysInTheFuture + durationInDays, 'days')
    .hours(hours)
    .minutes(minutes)
    .seconds(seconds)
    .millisecond(milliseconds);

console.log("reservation_start_at: " + reservation_start_at);
console.log("reservation_end: " + reservation_end);

pm.environment.set("reservation_start_at ", reservation_start_at);
pm.environment.set("reservation_end", reservation_end);

It will set the environment variables reservation_start_at and reservation_end, which you then can access in the request body:

{
   "name":"IronMan",
   "phone_number":"555555555",
   "number_of_guest":10,
   "tables":[
      2
   ],
   "reservation_start_at":"{{reservation_start_at}}",
   "reservation_end":"{{reservation_end}}"
}