Which is the first date of ISO 8061 format? Is it by Georgian Calander (1582-1-15) or 0001-1-1 ???
Which is the last date? I guess it must be 9999-12-31. Am I right???
The citations given in Wiki are not proper.
The practical limitation isn't in the ISO format at all but in the systems that use it. Different databases, for example, implement system specific limitations which are not even consistent across different releases of the same database.
In practice there is no alternative to RTFM.
For an example of some choices see this page explaining why some systems chose a 1753 cutoff (this was when the UK adopted the Gregorian calendar).