this is perhaps more of a plea for someone to kindly tell me of a program that already does this...
quite simply: a calculator with the usual basic functions but it works upon TIME format input, i.e. you can add 01h 33m 11s to 00h 56m 28s and obtain the result in a similar time output display.
i've had a look around and found 'time calculator pro' but it's not freeware - okay it's cheap - but i would have thought this kind of program would be a freeware thing somewhere.
of course, anyone willing to code it up from scratch would be my hero.