Calendar

BCE
BCE, meaning Before the Common Era, is a naming convention commonly used in academic circles to identify dating periods prior to the estimated birth of Jesus (traditionally, BC).

CE
CE, meaning Common Era, is a naming convention commonly used in academic circles to identify dating periods that have occurred after the estimated birth of Jesus (traditionally, AD).

a.
a. is the abbreviation for after, in the sense that a particular event occurred "after" a given year.

b.
b. is the abbreviation for before, in the sense that a particular event occurred "before" a given year.

c.
c. indicates circa (from Latin, meaning "around, about") and is used to express an event occurring "around" a given year.