Circadian rhythms establish a synchronization between the body’s metabolic processes and behaviour.
For example, the circadian rhythm helps to release the hormones on time basis, stimulate the appetite and sleep centers at regular intervals.
Due to the association between time and behaviour, it is easier to recall the event at the same time in the circadian cycle, which previously occurred.
So, research suggest that studying and taking the exam should occur at the same time for better remembering.