Conditioned responding that has been extinguished can spontaneously return when the conditioned stimulus (CS) is first presented after an extended delay. This spontaneous recovery of responding suggests that the memory of nonreinforced experience with the CS is impaired over the delay period. Rescorla (2007) provided evidence that this effect of time on nonreinforcement is not specific to extinction. He showed that a delay period can also reverse the reduction of responding established by a partial reinforcement schedule. Here we describe a series of experiments that attempted to confirm Rescorla's finding and additionally assessed the impact of the delay on another well-known consequence of partial reinforcement-the partial reinforcement extinction effect (PREE). Like Rescorla, we used a Pavlovian conditioning procedure with rats, measuring magazine activity during a CS that signaled food. Unlike Rescorla, we did not find that responding acquired under partial reinforcement spontaneously increased after a delay; however, we did observe a significant reduction in the PREE after that delay. We conclude that the passage of time has a selective effect on the retrieval of memories of nonreinforcement. Therefore, time produces spontaneous recovery by impairing retrieval of extinction memories but also weakens the PREE by impairing retrieval of memories of nonreinforcement that were acquired during partial reinforcement. (PsycInfo Database Record (c) 2022 APA, all rights reserved).