Question

I’m trying to convert event timestamp in a date, my code:

Calendar c = Calendar.getInstance();
c.setTimeInMillis(event.timestamp/1000000);//time in ms (timestamp is in ns)
System.out.println((new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(c.getTime()));

How come I get 1970-01-02?

Answer 1

I assume that you are using SensorEvent.timestamp. The documentation fails to mention that this is the awake time in nanoseconds since the last boot (comparable to SystemClock.uptimeMillis()), not time since Unix epoch. In short, it appears your device has been awake for less than two days.

Also, Calendar.getTime() returns a Date object and there is a Date constructor that takes milliseconds so you can shorten your code:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(sdf.format(new Date(event.timestamp / 1000000)));