We study the correction of errors that have accumulated in an entangled state of spins as a result of unknown local variations in the Zeeman energy ( B) and spin-spin interaction energy ( J). A nondegenerate code with error rate κ can recover the original state with high fidelity within a time tR�ħκ1/2/max(B,J)�independent of the number of encoded qubits. Whether the Hamiltonian is chaotic or not does not affect this time scale, but it does affect the complexity of the error-correcting code.