When a date is converted to a numeric, the value returned is the integer value for the internal stored date, which is encoded using the following formula:
(year - 1900) * 10000 + (month * 100) + day
Allowable date values range from AD January 1, 0001 to AD December 31, 9999.
For example, December 31, 1985 would be stored as the integer 851231; July 4, 1776 stored as -1239296; and March 30, 2041 stored as 1410330.
Conversion of DATE to DECIMAL(n,m) where the number of digits (n) is too small generates a numeric overflow error. Conversion of DATE to BYTEINT or SMALLINT generates a numeric overflow error if the value returned is outside the range of values that the data type can represent.
No error is generated on conversion of DATE to INTEGER or FLOAT.