timeCalc Advance is a calculator only for calculation of time. Ease of use was created in the first place simply anyhow. I think that it can use sensuously like the usual calculator. I think that it is useful for business lives in addition to calculation of the time in everyday life, such as calculation of overtime.
* The direction whose calculation of a second bit is unnecessary also has timeCalc Lite (with no advertising display).
timeCalc Advance is free software. Use at your own risk.