my 9800 att new,after i changed my battery ,it always ask me did the time is right?did all 9800 have the same problem?

It's not a problem. It's always been this way, though I don't know why you would see it all the time. What I've assumed is that when the battery is out for long enough the clock circuit eventually goes dead, and if the BlackBerry isn't able for some reason to get the time from the network when it boots up, then it will ask the user to verify the time. In my experience, it is rare for this to happen, but it does happen and always has (for me).