How to get total running time of a hard disk

Answer based on comments from @Zoredache:

Command is smartctl --all /dev/sdc and the section to look under is "Vendor Specific SMART Attributes with Thresholds", which has an attribute named "Power_On_Hours".

So command for just getting power on hours (runnning) is:

smartctl --all /dev/sdc | grep Power_On_Hours

Which can then show something like:

9 Power_On_Hours          0x0032   087   087   000    Old_age   Always       -       10171

The running time is thus: 10171 hours