My computer clock was out a full day?!

I just discovered that my computer clock was out a full day!
when updating LJ, it gave me an "incorrect time value"..
nope, I certainly didn't think I was trying to post in the past..
so I checked my date / time settings on the computer..
sure enough, they were a full 24 hours out..
this thing is certainly mind-boggling at times.. cheh!