Fechner Day is an annual informal observance celebrated worldwide every October 22. It honors Gustav Fechner, a German philosopher, physicist, and psychologist credited with founding psychophysics, the study of the relationship between physical stimuli and sensations. The day marks the anniversary of Fechner's significant insight into studying the mind through stimuli and perceptions, which he reportedly experienced on October 22, 1850. Psychophysicists commemorate this day, recognizing Fechner's contributions to the field, including the development of a psychophysical scale named after him. It is important to note that this observance should not be confused with the annual meeting of the International Society for Psychophysics, which is also referred to as Fechner Day but occurs in August.