Signs of the Time
"...and let them be for signs, and for seasons, and for days, and years" (Genesis 1:14).
One of the most timeless elements of human culture is calendar building. I humbly and gladly subscribe to the era designation of "A.D." (although various estimations of our Lord's Incarnation suggest that our current dating is miscalculated by between 4 to 7 years. Furthermore, my Christology would suggest the Resurrection as the "turning-point"). Nonetheless, this does not render useless other measurements...
Although "fictional," I particularly enjoy discussion about the StarTrek system of stardates.