unavailability in minutes from txt of the month

Hi all,
I have a big question and I need some help.
in the attached file there are the data when a process has gone down.
I need to take for a specific month (for example december 2012), day by day, the number of minutes that the process is unavailable and put them into a new txt file in the following way:

09.12.2012 process unavailable for  420 minutes
15.12.2012 process unavailable for "??" minutes
21.12.2012 process unavailable for "??" minutes
22.12.2012 process unavailable for "??" minutes
23.12.2012 process unavailable for "??" minutes
.......


Yes I know, this is difficult exercise   and maybe I'm asking too much but I hope that someone can help me.

thanks in advance