There is, and you're right, it was correct, do you remember if it was manually started or scheduled? They were logged differently, though it's been some time since I checked, could have changed.
Jun 13 13:12:29 Tower kernel: mdcmd (52): check
Jun 13 13:12:29 Tower kernel: md: recovery thread: check P Q ...
...
Jun 14 05:33:26 Tower kernel: md: sync done. time=58857sec
Jun 14 05:33:26 Tower kernel: md: recovery thread: exit status: 0
Start, duration and end (exit status 0 means it completed successfully, independent of finding sync errors or not) are always logged.