The most common reference to the current timeline within Toril. Before Calamity (B.C) Reprisents the years before the event that split the world. A vast war between kings and men holds no purchase on the intensity of the War of the Gods and Titans. As a result of this ancient battle between the gods, demihumans and angels, against titans, devils and demons, left the world asunder and was the creation of The Crag.
"... axes and blades of gods and titans split the land asunder" - Anonymous writer in a mythos of the history of The Reach
After Calamity (A.C) Refers to the time where things were rebuilding. The beginning of some calendars, though an unpopular stance as this was still quite long ago, and to write dates as long as 16,962 A.C is an unpopular choice.
This is where the destruction of the gods and titans had settled and life began to rise again in the newly formed world. This was a long time ago, however there are plenty of deep-rooted families that have history within the Era, including many of the founders of the nations we know today.
... though the land was torn asunder, life began anew with the age of elves and men." - History of Toril, 1432 C.E edition
C.E. aka Current Era refers to the time when society began to establish itself and nations had begun to truly form. This is the starting point for most calendars, by these standards it is currently 1635 C.E or in the After Calamity Calendar - 16,635