of time’ is to embed/graft/bury an approximate physical time in timeless formulation of quantum gravity. By ‘approximate’ we intend to satisfy the conditions (i), (ii) and (iii), at least approximately.

At present we have two ways of embedding the time in quantum gravity formulation and it is carried out through canonical quantization. The two ways of embedding the time are to prescribe it ‘before quantization’ or to do the same ‘after quantization’. Let us discuss the two procedures briefly. In quantum mechanics we follow the ‘constrained quantization’ in which the Hamilton of the system contains more variables than the physical degrees of freedom. For example, the classical general relativity constraint $H=0$ is converted to a constrained quantum equation by replacing $p_i=-i{\partial\over {\partial q_i}}$. After that one introduces the time by a prescription. This is known as ‘time after quantization’. Another attempt (of course less perused) is to solve the constraints before quantizing and to find the so called ‘internal time’ as a function of the canonical variables of general relativity such that this ‘time’ could serve as a time for the Schroedinger equation of quantized theory. This procedure is named as ‘time before quantization’. We follow the second one in 