I am trying to plot usage time for a device we use; data is in the following
format:

A B C
Online 23:27:39 12-Oct-08
Online 23:30:54 12-Oct-08
Online 23:34:09 12-Oct-08
Online 23:37:24 12-Oct-08
Offline 23:40:37 12-Oct-08
Offline 23:43:50 12-Oct-08
Offline 23:47:03 12-Oct-08
Offline 12:00:28 13-Oct-08
Offline 12:03:41 13-Oct-08
Offline 12:06:54 13-Oct-08
Online 12:10:10 13-Oct-08
Online 12:13:26 13-Oct-08
Online 12:16:42 13-Oct-08
Online 12:19:58 13-Oct-08
Offline 12:23:11 13-Oct-08
Offline 12:26:24 13-Oct-08
Offline 12:29:37 13-Oct-08
Offline 14:51:13 13-Oct-08
Offline 14:54:26 13-Oct-08

I'm trying with no success to plot online time by day and by time windows,
on a 24 hour scale.
Help and tips will be much appreciated.
Thank you.