The command
new SqlDateTime(1900, 1, 1, 0, 0, 0, 2000000);
throws a SqlTypeException. If the "bilisecond" parameter had referred to billionths of a second, or nanoseconds, this would have been a valid value. In fact, I have verified that they are microseconds, or millionths of a second - the following command:
new SqlDateTime(1900, 1, 1, 0, 0, 0, 500000)
results in a value with 500 milliseconds. Looks like somebody thought that a millisecond was a millionth of a second (it's a thousandth), and came with a "bilisecond" - see http://lists.ximian.com/pipermail/mono-patches/2007-May/091598.html .