  At the quantization of fields, due to the non-linear character of the time
reversal, the creation-annihilation operators for the negative frequency modes
should be replaced to the operators of antiparticles not directly in the field
operators, but in the operator products. For the standard minimal Lagrangians
(asymmetrical under the complex conjugated fields) it is shown that the charge
conjugation (C-) symmetry conditions for the Hamiltonian and the charge
operator lead to the identities for the operator products allowing one to
replace the negative frequency operator products to the positive frequency
ones. At the same time the operators in observables become normal ordered and
the zero-point energy does not appear. Only the symmetrized under the field
operators Lagrangians lead to the zero-point energy. The confrontation by the
experiments of the such C-symmetric quantization of fields and the solution
some of the vacuum energy problems are discussed.
