What is time ? My maths is so rusty its almost non existant. I'm looking at the energy to mass equivalence formula and trying to work out an equivalent 'unit of time'. With my poor maths I get; e=mc^2 e^(1/2)=m^(1/2)* c [In terms of units] e^(1/2)=m^(1/2)* (d/t) e^(1/2)*t=m^(1/2)* d t= d * m^(1/2) / e^(1/2) So in terms of units, time is related to distance ( einsteins spacetime ) multiplied by a 'small part' of mass over energy. Is doing this valid at all ?