Clock propagation delay between arrival and required path

The models have variation for best case and worst case process, voltage and temperature (PVT). To make TimeQuest run faster (by faster I mean wall clock time) at a specific PVT, TimeQuest looks at the specific case - for setup analysis, the launch clock comes as slow as possible and the latch clock comes as fast as possible and for hold time analysis, the launch clock comes as fast as possible and the latch clock comes as slow as possible. So even for the same path before it branches, you see different delays in the same path (I know this is strange). The amount of calculation and time required to resolve this to subtract the common path difference out. Some timing tools (like Primetime from Synopsys) subtract this out if you turn on the option, but the run time goes way up. The feature is called common clock pessimism and is rumored to be added to future versions of TimeQuest.