The 100th century of the anno Domini (common) era will span from January 1, 9901–December 31, 10000 of the Gregorian calendar.

All these dates are in a uniform time scale such as Terrestrial Time. When converted to our ordinary solar time or Universal Time, which is decidedly non-uniform, via ΔT, the dates would be a couple of days earlier. Furthermore, they are only astronomical dates, so they are given in the astronomical format of Year Month Day, which allows them to be ordered.

9966 August 11: Simultaneous total solar eclipse and transit of Mercury.

Software that encodes the CE / AD calendar year of a date as a four-character binary-coded decimal will no longer be able to encode the contemporaneous date. This problem may possibly occur from midnight on January 1, 10,000.

On January 1st, 10000, The Holocene Calendar will be entering their 3rd Deca-millennium while the Gregorian Calendar will be entering their 2nd Deca-millennium at the very end of the 100th Century in the year 10,000. The Gregorian Calendar will be in the year 10,000 and the Holocene Calendar will be in the year 20,000.