We study the almost periods of the eigenmodes of flat planar manifolds in the high energy limit. We prove in particular that the Gaussian Arithmetic Random Waves replicate almost identically at a scale at most ℓn := n − 1 2 exp (Nn), where Nn is the number of ways n can be written as a sum of two squares. It provides a qualitative interpretation of the full correlation phenomenon of the nodal length, which is known to happen at scales larger than ℓ ′ n := n −1/2 N A n. We provide also a heuristic with a toy model pleading that the minimal scale of replication should be closer to ℓ ′ n than ℓn. Contents 1. Introduction 1 2. Almost periodicity and replication 6 3. Dirichlet's theorem for almost periodic fields 13 4. Replication of the nodal lines 15 5. Optimality of Dirichlet's approximation theorem 19 6. Appendix 20 References 28