Busybox has support for the "-newer" construct, which checks if a file's modification time is newer than another file's. In findutils there's a "-newerXY" construct, with X and Y can be 'a' (last access), 'B' Birth time, 'c' (last change time), 'm' (last modification time), or t (timestamp); t being only the final argument and being for a literal timestamp. It's used as "-newerXY FILE" or "-newXt timestamp". In gentoo, they regularly use this construct. For example, their package manager defaults to checking "-newercm FILE" (change and modification). Similar functionality would be a welcome addition.