The pineal gland, also known as the pineal body, the third eye, conarium or epiphysis cerebri, is a small endocrine gland in the vertebrate brain.

It produces melatonin, a serotonin derived hormone, which affects the modulation of sleep patterns in both seasonal and circadian rhythms.

Human brain responding to the stimuli of seasons and time:

The pineal gland enables the human body or mindset to be to follow, and also be sensitive to the circadian rhythm which pertains to the role of responding to the stimuli of seasons, time, day, night, feasts or festivals and annual seasonal activities, which occurs in within the seasons of winter, summer, spring and autumn. 

The work of the pineal gland also includes the regulation of the biological clock, mood, appetite, and sleep. Serotonin which is produced by the pineal gland has some cognitive functions, including memory and learning.

Pineal gland also known as the third eye:

The other name which has been given to pineal gland is known as the third eye, (the eye which enables the human subconscious to visualise or see a vision, dream, imagine or detect information which is in form of frequencies, subliminal messages, environmental energies, radio waves, electro-magnetic field etc).

Its shape resembles a tiny pine cone (hence its name), and it is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join.