Amusing question, but a rather incomplete explanation.
The storage format ensures that the binary max and the datetime max will be the same date (as the datetime and its binary conversion have the same order). However that elimiates only two of the four rows. So now we need to know which of the remaining two rows will be maximum in binary order for date, and the only way to do that is to compute enough of the binary representations of the two candidate dates to see. The explanation ought to suggest at least one means of doing that.
Of course for this question the easiest way would be just to run the code - and I suspect quite a few of the 75% of answers (up to now) that are correct are the result of that approach.