You might be thinking to yourself, "what are those little stars doing in this design? Isn't it sunset?" and the answer is yes it is sunset and yes it would be quite a sight to be able to see the stars as the sun sinks below the horizon... but it's not impossible. Every 187 years in the Baja, on one late summer evening known as el dia de la puesta de estrellas, due to unexplainable atmospheric phenomena, the stars and the sun are visible together in all their glory.
Did we completely make that up? You'll just have to get the shirt and wait for the next atmospheric event in 2073 to find out.