The Cogs of Time, also known as the Gears of Time, the Gears of Destiny and the Celestial Watch was an attempt to create a workable explanation for the many uses of travel between timeframes and dimensions in the WatchmeX universe.
Visualised as a giant glowing blue series of interconnected cogwheels, Dr Manhattan theorized that not only is his unique precognition tied into the workings but that every available reality is intrinsically bound to its movements. Thus one character's journey to the past will cause the cogs to shift in relation and prevent any resultant temporal paradox. Despite this, with every timetravel event, the wheels continue to expand, adding to the established theory of a new alternate universe created with each trip.
Unknown to the characters within the book, the Watch-Belt and later the Watchback machine are fueled directly from the energy derived by the movement of the great wheels, meaning the more the technology was used, the more powerful it would become. Eventually it is said that at some point in the future the Watchback machine would become the foundation for the Cogs of Time itself.
The Cogs of Time themselves are basically an in-joke created by the writers on a whim as a random explanation for the inner workings of the WatchmeX universe as well as a watch-related play on words.