<Tr> <Td> temperature </Td> <Td> kelvin </Td> <Td> </Td> <Td> triple point of water, absolute zero </Td> <Td> Boltzmann's constant, k </Td> </Tr> <Tr> <Td> amount of substance </Td> <Td> mole </Td> <Td> mol </Td> <Td> molar mass of Carbon - 12 </Td> <Td> Avogadro constant N </Td> </Tr> <Tr> <Td> luminous intensity </Td> <Td> candela </Td> <Td> cd </Td> <Td> luminous efficacy of a 540 THz source </Td> <Td> same as current SI </Td> </Tr> <P> The mole was subsequently added to this list and the degree Kelvin renamed the kelvin . </P>

Which would be considered an instrument or method of measuring relative time