In learning, repeated experiences might be integrated individually as they occur, or they might be combined within dedicated time windows, possibly promoting quality control. I will discuss recent findings from our laboratory providing evidence that in Pavlovian, incremental, and incidental learning, related information acquired within time windows of 5 hours (time units for learning) is combined to determine whether and what mice learn. Trials required for learning have to occur within 5 hours, when learning-related shared partial cues can produce association and interference with learning. Upon acquisition, cFos expression is elevated during 5 hours throughout specific system-wide neuronal assemblies. Time unit function depends on network activity and local cFos activity, which is required for distant assembly recruitment through network activity and distant BDNF. Activation of learning-related cFos assemblies is sufficient and necessary for time unit function. Therefore, learning processes consist of dedicated 5-hour time units, involving maintenance of specific system-wide neuronal assemblies through network activity and cFos expression.