This tool can roughly determine the best location to fly to to get access to the McDonald's breakfast menu, based on flight time and whether it will be breakfast time once you arrive.
It is perhaps better explained with an example: it's 1700h (5 PM) in Tokyo, and you want a McMuffin, but the breakfast menu isn't going to open for another 13 hours. You can't afford to wait that long, but where else can you go? The answer, as this tool will tell you, is Honolulu. You'll arrive around 0616 local time, ready to stride into a McDonald's and get breakfast. In Tokyo, it's only 0116, and you would have had to wait hours longer for your McMuffin.
Distances are rough estimates. Flight times and prices are very rough estimates. DST is not factored into the calculations. Prices and participation may vary.