A little help with time calculations

[iminal]

I am trying to make a very simple program and am very new to the whole
programming thing. my program is supposed to ask a user for any time in
the for format XX:XX:XX and then ask for a time corrrection to add or
subtract to this. my only problem is that once the user inputs the time
and the correction its adding it like it was 100 not to 60 any help?