When is National Right Handers Day?

There is no official right handed day, so since August 13th is National Left Handed day that would make every other day of the year National Right Handers day.

If there needs to be a good reason to have one there is always the story of what happened on Sunday September 3. 1967. This was the day Sweden switched to driving on the RIGHT HAND side of the road. Known as Högertrafikomläggningen, or the Right-Hand Traffic Diversion.
It is also been theorized that right handed people live longer than their lefty counterparts, but that theory has been challenged.