The most common clave pattern used in Cuban popular music is called the son clave, named after the Cuban musical genre of the same name. Clave is the basic period, composed of two rhythmically opposed cells, one antecedent and the other consequent. Clave was initially written in two measures of 2 4 in Cuban music.
Eon, a variation of aeon, is defined as a unit of geological time equal to a billion years, or a very long period of time. An example of an eon is the unit of measure used when talking about how long ago the solar system was created.
Since this question is posted in Astronomy, I will assume that the answer of eon = 109 years is the most appropriate, however it is not the most common. The term eon (or aeon) is frequently used as a term for a very long but un-specified time period, much the same way forever and ages are used.