0.123 = - log T T =

if you mean log to the base 10, then 0.123 = -logT means that T = 10^-0.123 or 

$${\mathtt{T}} = {{\mathtt{10}}}^{-{\mathtt{0.123}}} \Rightarrow {\mathtt{T}} = {\mathtt{0.753\: \!355\: \!563\: \!733\: \!717\: \!4}}$$