We develop the harmonic analysis approach for general second order par
abolic operators in divergence form (i.e., allowing for time dependent
coefficients) in the setting of a class of time-varying domains. More
precisely we prove doubling properties of the associated caloric meas
ure, we define and study the kernel function and prove the relevant es
timates for the non-tangential maximal function and the area integral.
All these tools are considered in order to prove some perturbation re
sults for the Dirichlet problem with data on the lateral boundary of o
ur time-varying cylinder.