This tool calculates the distance between two points on earth based on the "haversine formula", as the earth is an ellipsoid rather than a real sphere, this formula is extended. The flight distance differs in respect to the flight height from the actual ground distance.
The calculated flight time is obviously an estimate because it is not possible to know all circumstances (weather or wind) and the real flight route. But this tool tries to get as close as possible to the real conditions. Generally it differentiates between short-distance and long-distance flights.
Start and destination airports are matched to a world-wide timezone map, although this map does not know about daylight-saving times.
All calculated data are estimates, therefore we can not garantuee that these are correct.