On Fri, Mar 4, 2011 at 3:04 PM, Denniston, Todd A CIV NAVSURFWARCENDIV Crane <todd.denniston at navy.mil> wrote: [snip] > If your hwclock is off by a lot when it comes up I believe it is from > one of the following: > A) bad cmos battery. > B) poor cmos clock > C) confusing info in /etc/adjtime due to using both hwclock --adjust [at > boot] and ntp (long story, but it is due to both tweaking the clock > without coordination between them). > D) booting a different OS with different ideas of timezones. > E) manual tweaking of time via bios. [snip] good list.. I'd also add "F) Running inside a virtual machine." The VMWare clock skew can be enormous. On some systems it drifts by a minute per hour if not adjusted via ntp.