Before the Present (BP) is currently based on the year 1950 AD. When they constructed this dating system in the early 1950s, they should have been a little more forward-thinking and should have chosen a much nicer, rounder number like the year 2000 AD to use as a reference point. Using this millennial number as a reference point instead would have resulted in less mental overhead when attempting to accurately perceive an event’s distance from the present.
Nevertheless, a fundamental requirement to creating a timeline is to determine which point on that timeline to use as a beginning reference point. There is nothing particularly special about the years 1950 AD or 2000 AD other than that they are nice round numbers.
It would be logical to use, if one could be found, a single, fairly recent, unique, and instantaneous event in human history as a reference point (zero point) for a timeline on which all other years would be based. No fairly recent, natural events in human history such as the discovery of fire, the invention of the wheel, the development of agriculture or anything else readily appears to qualify as an event fit to function as a precise and unique reference point for the timeline of history. Looking to the supernatural world, something as significant as God intervening in the natural world would definitely be a significant time marker for history. In fact, we currently use a variation of this theme (the birth of Jesus Christ) as the basis of the current BC/AD dating system. Jesus’ birth, however, was only the necessary prerequisite for His ultimate purpose–His death and resurrection. Ideally, Jesus’ resurrection should be the reference (zero) point of history because that event marks the point at which God finished the purpose for His supernatural intervention on this planet. But because there is currently as much confusion about the exact date of His resurrection as there is about His birth, it may not be worth the hassle of shifting our calendar system over by 30 or so years unless we get a higher confidence on a more specific date.
Regardless of whether or not we choose to change the reference point of our current timeline, there is still a significant problem related to the the absence of a zero year on this timeline. Every properly built number line must include a zero point between negative and positive numbers. Thus, when counting years across this BC/AD transition, it is not possible to simply add the BC years to the AD years because the sum would always erroneously include an extra year. For example, 2 BC + 2 AD appears to equal 4 years, but really adds up to only 3 years. To fix this problem and make our timeline a true number line, it would be necessary to add a zero year immediately following the reference point event. Therefore, the 365 days immediately following the reference point (such as the Resurrection) would be called the year zero, or Y 0. The following year would be year 1 or Y 1. And the year immediately preceding the reference point would be year negative 1 or Y -1. All subsequent years would naturally follow a normal number line. In fact, because this new system is basically a normal number line, we could do away with the BC/AD tags and just refer to years by their numbers alone, for example, 2005AD could be the year 2005 or Y 2005 (the “Y” would signify that the following number refers to a year). Counting back in history across the transition would be less confusing than it is currently because it would be a simple matter of adding the negative and positive year numbers.