Does anyone know of a time calculator for OSX?

I'm looking for a calculator that allows me to do this kind of math with times

```
HH:MM:SS
----------
01:15:58
- 00:15:00
+ 02:30:00
----------
= 03:30:58
```

Ofcourse the actualy calculations i'm looking to do are a little more complex and involve alot more data but basically adding and substracing is all it should do.

`03:30:58`

at the end, right? – Daniel Beck♦ Nov 30 '10 at 11:30