How to read the linux timestamp in the output screen?

Question

I guess my linux (Ubuntu) box is crash. It printed out:

[422473.440904] Call Trace:
[422473.440937]   [<fffffffff81073655>] ? wq_worker_sleeping
[422473.449036]   ...
....
[422473.609529] CR2: ffffffff8

My question is: is [422473.609529] the time when the crash happened? What time is that? It is not the Epoch Unix time (currently 1384301380). If it is "second", then that is 117 hours, not actually mean anything.

--add picture

Answer 1

Means:

422473.440904
   |      +----------- micro sec portion
   +------------------ seconds since boot

The timing information is called printk() times. Check this or this for further reference. Btw, nice image :)