Tracks a true solar day? Is there actually a scientific definition of when a day starts and ends? As far as I can tell skimming Wikipedia, it's simply 86400 seconds.
Certainly by my body clock, a "true solar day" is when I'm on DST.
Midday GMT is defined to be when the mean sun is directly over the prime meridian.
("Mean sun" as opposed to "apparent sun" because of the Earth being a naturally occurring celestial object, rather than an idealised mathematical model. See http://en.wikipedia.org/wiki/Equation_of_time .)
