When I worked with Clearcase (which is terrible in many ways, this is just one), one of its nice features was that it changed file timestamp to the timestamp of commit, not the timestamp it was changed on developer's machine. The commit timestamp may be after previous commit but also before the compiled object file. Because of this, the only way to do a reliable build was to start from scratch. Which took 45 minutes.

Ceterum censeo, Clearcase must be destroyed.