Maybe we're talking past each other? A bar is a time period with a start and an end. A price quote is an event that happens at a certain time. Only price quotes have timestamps.

You can also assign a timestamp to a bar, but that is only a convention. With Zorro, it is the current time at the end of the bar. Other software might use the bar start time or middle time.

I'm working from an old memory so this may be totally wrong, but... doesn't the IB interface "batch" ticks and send them out in bursts? If so, then maybe the bursts are normally coming every 2-3 seconds?