 In order for a thing to change from having \(P_1\) at \(t_1\) to having \(P_2\) at \(t_2\) it must evidently persist at least from \(t_1\) to \(t_2\), but the events usually supposed in discussions of passage are instantaneous events, which have no duration at all. They can not undergo qualitative change. It is sometimes argued that the properties that make up the A-series (and so change of which represents passage) are special properties, which even instantaneous events can gain and lose, but this is special pleading. As noted above, physics has so far no need of such special properties and such special change and so is unlikely to be sympathetic to this special pleading.