ARKit: What does the ARFrame.timestamp represent?

Question

In ARKit, ARFrame.timestamp is a TimeInterval with values such

185726.884258291
185726.91759425
185726.950930291
...

I'd like to get the unix timestamp from these values, but they don't look familiar. What do these numbers represent?

Answer 1

These numbers represent uptime at the moment the frame has been captured, see it yourself by calling

NSTimeInterval systemUptime = [[NSProcessInfo processInfo] systemUptime]; 

Methods and thoughts about converting it to a Unix Timestamp.