I have a simple code, I record the time when the user hits a button and subtract that time from the current time. It should give me the difference.

The funny part is that if I print my vars they are correct but when I make the subtraction the result is the year 1969 the time the system takes as reference.

This is my code:

```
// I register this time to later compare to the current time.
startTime = System.currentTimeMillis().toDouble()

timer = Timer()
timer.schedule(timerTask {
    runOnUiThread {
        advanceTimer()
    }
}, 0, 60)

fun advanceTimer() {
//Total time since timer started, in seconds
val currentTime = System.currentTimeMillis().toDouble()
time = currentTime-startTime

}

```

This is what the console prints:

D/startTime: 2020:12:20:21:27:39:78

D/currentTime: 2020:12:20:21:29:49:21

**D/time: 1969:12:31:18:02:09:42**

Can somebody help me, please?