Heisenberg representation: why position operator has no explicit time dependance?

In Heisenberg representation we have:
$$frac{d}{dt}A_H(t)=frac{1}{ihbar}left[A_H(t),H_H(t)right]+frac{partial A_H(t)}{partial t} (1)$$
where I use the subscript $H$ to make as explicit as possible that we are working in Heisenberg representation. If we apply $(1)$ to the position operator $hat{q}_H$ we get:
$$frac{d}{dt}hat{q}_H=frac{1}{ihbar}left[hat{q}_H,H_H(t)right]$$
or at least this is what my lecture notes said. This derivation uses the fact that the position operator has no explicit time dependence:
$$frac{partial hat{q}_H}{partial t}=0$$
I do not understand why this has to be true. How do we know that the partial derivative of $hat{q}_H$ has to be zero in Heisenberg representation?

Since in the Schrödinger representation the states can explicitly evolve with time, changing their "relation" with the position operator, I would expect the same in the Heisenberg representation but mirrored onto the operators.