I turn off my computer by turning off the power bar which is connected to the power outlet on the wall. The power bar LED goes from red to off.
The next time, at least several hours, I turn on my computer by turning on the power bar, the computer clock lose time for several minutes or more. After I change the computer clock to the right time, it will run correctly until I turn off the computer. Then when I turn on my computer, it will lose time again. The exact amount is different each time, from several minutes to more than 10 minutes.
What is the problem?

such a slow trickle of time -- that's kinda wierd, but my first thought is to replace the battery...