Added Current Century Year Mapping

There are a few ways to map two digit years, here is the one my clients pick most often... mapping the two-digit year to the current century

Other methods are

10year+ previous century - so 23 would become 1923 because we are in 2013 but 15 would become 2015 - Investment tracking systems

pre-y2k 1900 - suggests that only pre-y2k data is being imported and needs 19 added before each date so 01 == 1900 99 == 1999 - used by businesses on legacy imports

context set century - first you set the century, then it appends the decade and year so if I set the context to be 1700 it splices 17 before all dates and appends decade and year - Museums, complex historical data-sets. The added ycc mapping is a variant of csc mapping

Hope this helps someone other than me