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.
Year 10,000 problem
The Long Now Foundation is attempting to foster the custom of writing years with five digits, so that the year 2022 would be written as "02022". This would preempt the Year 10,000 problem, but would in turn be susceptible to the "Year 100,000 problem".