10:10 is known as happy time! Why is it known as such? Why because when the hands on a watch point at the two numbers it looks similar to a happy face.
Strange but true, for most catalogs(Sears, Target, Wal-Mart, etc.) have all their clocks set at 10:10 to make them look happier. This method has even stretched to digital clocks.
Mblase has his own theories on a 10:09 setting involving symmetrical hands. However, one should keep doubt in mind. For a theory on a perfectly timed watch should definitely be doubted, because many watches can have their hands manually moved.