Dashboards don't updated based on conditional formatting of cell

That is what I am doing — in the underlying data sheet, the conditional format "highlights events posted in the last two days". The sheet feeds into a report. That report is part of a dashboard. Sometimes (I haven't figured out what causes it), an item on the dashboard will be highlighted, even though it falls well outside of the "last two days" dictated by the underlying conditional formatting on the sheet. For example, I have one right now that was posted 7 days ago, but the conditional formatting is still appearing on the dashboard (but does not appear on the underlying sheet or report).