9 mya
The molecular clock is based on the mutation rate of biomolecules in order to estimate how long ago two organisms diverged from each other. The data that's used to determine the mutation rate is nucleotide or amino acid sequences. By comparison of this sequences, it can be defined how different they are and that's what will determine the mutation rate. If the mutation rate is high then the two species are far distant, if the rate is low, the two species are closer.
