How do you obtain the maximum possible date in Oracle?
From the 11g docs:
Oracle Database can store dates in the Julian era, ranging from January 1, 4712 BCE through December 31, 9999 CE (Common Era, or 'AD').
http://download.oracle.com/docs/cd/B28359_01/server.111/b28318/datatype.htm#i1847
I do not know of a function but according to this article:
Oracle 7: from January 1, 4712 BC to December 31, 4712 AD.
Oracle 8: from January 1, 4712 BC to December 31, 9999 AD.
Oracle 9: from January 1, 4712 BC to December 31, 9999 AD.
PL/SQL: from January 1, 4712 BC to December 31, 9999 AD.