You can also create a date with the current local date plus the number of miliseconds you need to add as Expire time

import java.util.Date;

long expiremilis = 60000l; //  1 minute
// Expires in one minute from now
Date expireDate = new Date(System.currentTimeMillis() + expiremilis);

Or the same with a calendar

long expiremilis = 60000l; // 1 minute
Calendar expireDate= Calendar.getInstance();
// Expires on one minute from now
expireDate.setTimeInMillis(System.currentTimeMillis() + expiremilis);

If you use an existing Date object you can do:

import java.util.Date;

long expiremilis = 60000l; // 1 minute
// Expires on one minute from the date object date
Date expireDate = new Date(myDate.getTime() + expiremilis);

And with an existing Calendar Object

long expiremilis = 60000l; // 1 minute
Calendar expireDate= Calendar.getInstance();
// Expires on one minute from the calendar date
expireDate.setTimeInMillis(myCalendar.getTimeInMillis() + expiremilis);

java.time

The java.util Date-Time API and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern Date-Time API^*.

Demo using java.time, the modern API:

import java.time.Instant;

public class Main {
    public static void main(String[] args) {
        Instant createdOn = Instant.ofEpochMilli(1_622_800_000_000L);
        System.out.println(createdOn);

        Instant timeout = createdOn.plusMillis(50_000L);
        System.out.println(timeout);
    }
}

See this code run live at IdeOne.com.

Output:

2021-06-04T09:46:40Z
2021-06-04T09:47:30Z

An Instant represents an instantaneous point on the timeline in UTC. The Z in the output is the timezone designator for a zero-timezone offset. It stands for Zulu and specifies the Etc/UTC timezone (which has the timezone offset of +00:00 hours).

So, the solution to your problem would be:

Instant createdOn = token.getCreatedOn().toInstant();
Instant timeout = createdOn.plusMillis(token.getExpiresIn());

Check documentation of Date#toInstant to learn more about it.

Learn more about java.time, the modern Date-Time API^* from Trail: Date Time.

^{* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.}

Calendar is a fairly expensive Date object, and it functionality is not the best. If you want an all purpose Date object I suggest looking at JODA Time and it has a function which does what you want.

However, a simpler Java Date object is the Date class as @Dubas indicates.

Even simpler for the type of operation you are performing is to use a long. This is also much faster.

long timeoutMS = token.getCreatedOn() + token.getExpiresIn(); 

I use long (in GMT) for all my dates and only use Date for the presentation layer. ie. when you want to convert the date to Text.