why 10-10 is shown in every clock?
Although there are urban legends that clocks are set at 10:10 because it commemorates the death of John F. Kennedy or Abraham Lincoln, the real reason is marketing. Most clocks or watches with hands have the manufacturer's name or logo near the top of the face under the 12. By placing the hands of the clock at 10:10, the hands frame the manufacturer's name. Timex used this marketing approach in its 1960s advertisements. If the logo is near the bottom of the clock face above the 6, the hands may be postioned at 8:20. However 8:20 is less common because some feel that the clock is "frowning" when the hands point down.