proleptic

1. (of a calendar) Extrapolated to dates prior to its first adoption; of those used to adjust to or from the Julian calendar or Gregorian calendar.Examples: "The Julian proleptic calendar is formed by applying the rules of the Julian calendar to times before Caesar's reform, and the Julian date (JD) specifies the particular instant of a day by ending the Julian day number with the fraction of the day elapsed since the preceding Greenwich noon."; "The proleptic Gregorian calendar is produced by extending the Gregorian calendar backwards to dates preceding its official introduction in 1582."; "The .NET epoch is midnight at the start of January 1st, AD 1, although that's AD 1 in a proleptic Gregorian calendar, which refers to even more complexity we haven't talked about yet."