Astronomical year numbering
Cassini gave the following reasons for using a year 0:
Fred Espanak of NASA lists 50 phases of the moon within year 0, showing that it is a full year, not an instant in time. Jean Meeus gives the following explanation:
Although he used the usual French terms "avant J.-C." (before Jesus Christ) and "après J.-C." (after Jesus Christ) to label years elsewhere in his book, the Byzantine historian Venance Grumel used negative years (identified by a minus sign, −) to label BC years and unsigned positive years to label AD years in a table. He did so possibly to save space and put no year 0 between them.
Vehicle identification number
One consistent element of the VIS is the 10th digit, which is required worldwide to encode the model year of the vehicle. Besides the three letters that are not allowed in the VIN itself (I, O and Q), the letters U and Z and the digit 0 are not used for the model year code. The year code is the model year for the vehicle.