My clock won't reset to the right time after I reboot my Nook!
It was strange. As I said, my clock is too fast by 4 minutes.
After I used two busybox commands to set date/time and hardware clock as stated in
http://nookdevs.com/Tips_and_tricks#..._Date_.26_Time
the clock stayed at the latest time for 4 minutes until the internal clock catch up; and then the time display is running again. I turn if off and on again and the clock is still correct.