Time
Abbreviation and Definitions 

 B.C.: 
  
the abbreviation of "before Christ"; in measuring time, this means years before the birth of Christ 

 B.P.: 
the abbreviation of "before the present" 

 B.C.E.:  
  Before Common Era
 


 A.D.:  
the abbreviation of anno domini, which means "in the year of our lord"; in measuring time, this means years since the birth of Christ 

 CE:  
 Common Era


 m.y.a. : 
 millions years ago