Particular time-scheduled works are nowadays increasing in frequency and diffusion, beside typical shift-work. As sleep researchers know in details, clinical consequences of such atypical time-schedules include: sleep loss, daytime vigilance impairment, decrease in neurocognitive performances, increased risk of accidents (in work environment or while driving) and biological effects, such as metabolic and endocrine impairment and immunity decline. Moreover, shift-work has been associated with breast cancer, due to a circadian disruption and to a nocturnal suppression in melatonin production. Despite overwhelming evidence, there is only a mild awareness of the risks and costs related to sleep loss and circadian disruption. In addition, a great amount of sleep disorders produce daytime sleepiness and workers often suffer from an impaired vigilance due to a misdiagnosis or a neglected sleep disorder. Occupational health physicians need to be educated about the importance of detecting impaired alertness in workers. A more correct organization of time-schedules is mandatory to obtain a reduction of occupational related health problems and to bear the modern "24-hours society".