The soap opera, Days of Our Lives, has as their catchphrase,  “Like sands through the hourglass, so are the days of our lives.” The meaning of that catchphrase is clear–life passes by very quickly.  Life measured by the grains of sand slip through one side of the hourglass to the other in a flash.  The hourglass symbol on a gravestone, often shown with wings, represents the same thought of time fleeting by quickly.