Cells have an entire range of clocks for tons of purposes. Including a number of "death clocks" tracking a number of things, from passage of time since last cell division (including the famous telomeres), to amount of energy passing through the cell and a lot of more specialized clocks as well. (death clock meaning the cell will self-terminate if the clock runs down)

Just listen to your heartbeat and think again whether your cells don't track the passage of time.