###### Abstract
Subjects' sleep quality, alertness and mood were evaluated using the Pittsburgh Sleep Quality Index, Karolinska Sleepiness Scale and Positive and Negative Semantic Scales. The researchers concluded that daylight exposure before awakening in summer significantly influenced subjects' alertness, mood and deep sleep duration, but it did not impact these indexes in winter [14]. This research demonstrated that daylight affects occupants' circadian systems, but it did not measure the spectrum of light, which changes throughout the day and across seasons, due to equipment limitations. Some studies have compared the effects of daylight and electric lighting on human circadian systems. [PERSON] et al. [15] found that subjects exposed to daylight during the daytime were more alert at the beginning of the evening than those lit by electric light. They further reported that subjects who were exposed to daylight earlier in the day felt sleepy later than those illuminated by electric light [15]. However, this study did not report sufficient circadian related metrics for the lighting conditions. [PERSON] et al. measured irradiance, correlated colour temperature of the light, vertical illuminance at eye height, and horizontal illuminance 0.8 m above the floor in a classroom on two typical winter days, under daylight conditions and electric lighting conditions [16]. Their study provided valuable empirical data comparing the circadian effects of daylight and electric light. The results demonstrated that daylight led to greater calculated melatonin suppression. However, the daylight data were collected by pointing instruments \"on the section of the sky visible through the classroom windows\" [16]. This may overestimate the effect of daylight in real applications because occupants do not always face windows, and reflections off large internal surfaces in buildings (e.g., walls) may alter the spectrum of light. In [PERSON] and colleagues' research [17], each participant wore an Activatch-L, which is a wrist-worn device equipped with a photodiode, for two weeks. The intensity and duration of light exposure were recorded when participants performed normal daily activities. The researchers found that low amounts of daylight exposure in offices led to reduced sleep duration, poorer sleep quality and lower activity levels [17]. However, they acknowledged that the light exposure data collected by devices worn on wrists may not fully represent the light reaching the retina. Additionally, the daylight and electric light were not analysed separately due to equipment limitations. Therefore, they suggested that future research collect spectral measurements of daylight and electric light independently using devices located in positions similar to those of people's eyes [17]. Given the widespread uses of computers, tablets and mobile phones [18], these increasingly bright screens, such as those with a peak luminance of 1000 cd/m\({}^{2}\)[19], likely also play an important role in influencing occupants' circadian rhythms. [PERSON] et al. investigated office workers' task performance using a computer under three lighting conditions: 2700 K, 4000 K and 6200 K [20]. One of their conclusions was that 2700 K light can notably increase users' alertness, as the data showed that participants had the fewest typing errors in a typing test when illuminated by 2700 K. The authors noted that this result was not in accordance with other research in the scientific literature. It is commonly accepted that short wavelength light suppresses the production of the hormone melatonin, which should theoretically increase people's alertness. The authors explained that their findings might be caused by their small sample size (10 subjects). However, there might be other explanations, such as the light from the screens dominating the electric lighting, negating any differences in performance caused by the illumination that may be otherwise observed.