From the Airnautic Watch Company web site:
The guiding design philosophy of AirNautic® Watch Company is to separate day and night as the elemental parameters of the perception of time. The course of the sun determines our regeneration phases and influences the biological processes of all life forms on our planet. In extreme conditions under water, in space, in the labyrinth of a cave system, or in a polar night, the holistic information on time can save lives. Being able to easily and instantly read this information at a glance is part of the philosophy and design concept of the new AirNautic Watch Company.
How can you not want one of these!?