Year zero
Year zero does not exist in the anno Domini system usually used to number years in the Gregorian calendar and in its predecessor, the Julian calendar. In this system, the year is followed by . However, there is a year zero in astronomical year numbering (where it coincides with the Julian year ) and in ISO 8601:2004 (where it coincides with the Gregorian year ) as well as in all Buddhist and Hindu calendars.
1000
Year 1000 (M) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar. In the proleptic Gregorian calendar, it was a non-leap century year starting on Wednesday (like 1800). It was also the last year of the 10th century as well as the last year of the 1st millennium of the Dionysian era ending on December 31st, but the first year of the 1000s decade.