Wall clock time is pretty much only measured in practice as some offset relative to some repeating process, though (e.g. hours since start of day). Cells certa

Wall clock time is pretty much only measured in practice as some offset relative to some repeating process, though (e.g. hours since start of day). Cells certainly have processes that repeat on a daily basis, at different offsets from the beginning of the day; they may not actually be measured by counting ticks (the jury's still out on exactly how they do it, I think?), but the effect is similar.