I see a page on speedcubing.com devoted to this category, but what exactly does it mean?

http://speedcubing.com/records/recs_fun ... e2005.html

When we adjust the time from summer-time to winter-time.
If you start yor solve that night at 2:59.59 the time whold be 2:xx.xx when you stop solving. Your solvingtime is start-stop time and will be negative.

I thought it meant how fast you can scramble a cube

so you start your solve at 1:59:59 and you end it at 1:00:24. due to the hour time change your solve is negative 59:36

How about doing a solve while flying East across the International Date Line? You could have a solve of about negative 23h 59m --s!

I suggest you repeat that question should you ever meet Tyson Mao.

Man.... You guys are no help....

Why not just google for:
negative time rubik

First link is perfect:
http://cubefreak.hp.infoseek.co.jp/negative.html

Why google when someone will eventually answer? Besides, asking dumb questions keeps things lively. Thanks for the answer.