Why does HFT care where we are or how we're rotated in relation to the sun? So long as we all agree on what time it is, whether 12pm denotes high noon or not is arbitrary and irrelevant.
The only thing I can think of: a good HFT algo might be able to exploit leap seconds to somehow gain an advantage over those that are ignorant of them (or vice versa).
Valid point imho. Sad to see your comment turned to grey within as little as 8 minutes after you posted it.