Year zero
Historians have never included a year zero. This means that between, for example, and , there are 999 years: 500 years BC, and 499 years AD preceding 500. In common usage "anno Domini" 1 is preceded by the year 1 BC, without an intervening year zero. Neither the choice of calendar system (whether Julian or Gregorian) nor the era ("Anno Domini" or Common Era) determines whether a year zero will be used. If writers do not use the convention of their group (historians or astronomers), they must explicitly state whether they include a year 0 in their count of years, otherwise their historical dates will be misunderstood.
Panic in Year Zero!
After a harrowing journey, the Baldwins reach their destination and find shelter in a cave, while they wait for order to be restored. On their portable radio they listen to war news and learn what is left of the United Nations has declared this to be "Year Zero". Harry and Rick find that Johnson and his wife are their neighbors, but not for long; they are killed by the thugs.