Core formation timing is dated using short-lived (now-extinct) radionuclide chronometers active only in the earliest solar system. The 182Hf-182W system is uniquely suited for this because Hf is lithophile (stays in silicate mantle) while W is siderophile (partitions into metallic core), making the Hf-W isotopic system sensitive specifically to the timing of metal-silicate (core-mantle) separation, with a half-life (~8.9 Myr, here approximated as 6.0×10^6 y) short enough to resolve processes within the first ~30-60 Myr of solar system history.