Production slows when not logged in - Coinage

Just noticed an odd bug. I had been logging out and in when I needed to do something to save on my computer system resources rather than staying logged in all the time. I noticed that the coinage was not making coins when I expected it to. At first I thought I was getting my timings wrong, but then I tested it. I set a timer for 24 minutes as soon as the production started and then logged out. When the timer was almost finished I logged back in again. The coinage should have been almost finished in making coins but I found that there was still another 15 minutes until the next coin would be produced!

This bug doesn't happen when I am logged in, only when I am logged out. Is time not passing as fast when logged out? This problem doesn't happen with the timers on buffs